Word Family - Tree

May theme: Plants 🌱

Introduction

In which dryad and druid are basically the same word, trust and tryst, trees and truce. Plus horse racing history.

Teaser

tree, true, true, endure, druid, dryad, larch, derby, tray, tray

Full Text

Proto-Indo-European *drew- hard, firm, strong, wood, tree ^[1]
- Proto-Indo-European *droweh₂yéti
  - Germanic *trūwijaną
    
    North Germanic
    
    Old Norse trúa to believe
    
    Old East Norse
    
    Danish tro to believe, to think
    
    Old West Norse
    
    Icelandic trúa to believe
    
    West Germanic *trūēn
    
    Old English trūwian to trust, to have faith in
    
    Middle English trowen to trust, to judge, to think, to accept
    
    English trow
    
    Scots trow
    
    Frankish *trūen
    
    Middle Dutch truwen
    
    Dutch trouwen to trust, to marry
    
    Old High German trūēn / trūwēn
    
    Middle English trūwen to trust
    
    German trauen to trust, to marry
- Proto-Indo-European *drewéyeti? ^[2]
  - Germanic *trēwaną? ^[2]
    
    Germanic *triwwiz true, faithful
    
    East Germanic
    
    Gothic 𐍄𐍂𐌹𐌲𐌲𐍅𐍃 triggws true, faithful
    
    North Germanic
    
    Old Norse tryggr true
    
    Old East Norse
    
    Danish tryg safe, secure, easy, confident
    
    Old West Norse
    
    Icelandic tryggur safe, secure
    
    West Germanic *triuwī
    
    Old English trīewe / trēowe true
    
    Middle English treowe / trewe
    
    English true
    
    Scots trew
    
    Frankish *triuwi
    
    Middle Dutch trouwe
    
    Dutch trouw true, faithful, loyal
    
    Old High German triuwi
    
    Middle High German triuwe
    
    German treu loyal, faithful, true
    
    Germanic *triwwiþō promise, contract
    
    North Germanic
    
    Old Norse tryggð
    
    Old East Norse
    
    Danish trygd
    
    Old West Norse
    
    Icelandic tryggð loyalty, fidelity
    
    West Germanic *triuwiþu
    
    Old English trēowþ
    
    Middle English treuthe / trouth
    
    Middle English bitrouthen / bitreuthen
    
    English betroth
    
    English betrothal
    
    English truth
    
    English troth
    
    Scots trowth
    
    Germanic *triwwijaną to be faithful, to make faithful
    
    North Germanic
    
    Old Norse tryggja
    
    Icelandic tryggja to secure, to ensure, to insure
    
    West Germanic
    
    Old English trīewan / trēowan
    
    Middle English trowen to trust, to judge, to think, to accept
    
    English trow
    
    Scots trow
- Proto-Indo-European *druwós
  - Hellenic *drowós *drowón
    
    Classical Greek δροόν *droós droón strong, mighty
  - Italic *dūros
    
    Latin durus hard, harsh, vigorous, stern, unyielding ^[3]
    
    Latin duracinus hard-berried, stone fruit
    
    Central Romance
    
    Dalmatian drucno
    
    Italian duracina
    
    Western Romance
    
    Old French duraine
    
    Spanish durazno peach Latin American only
    
    Quechua turasnu peach
    
    French duracine type of peach
    
    Classical Greek δωράκινον dōrákinon type of peach
    
    Greek ροδάκινο rodákino peach
    
    Classical Syriac ܕܘܪܩܝܢܐ dōraqqīnā apricot, peach
    
    Arabic دُرَّاق durrāq peach
    
    Central Romance
    
    Italian duro hard, tough, harsh
    
    Insular Romance
    
    Sardinian duru hard, tough
    
    Western Romance
    
    Old French
    
    Middle French
    
    French dur hard, tough, harsh
    
    Spanish duro hard, solid, tough, cruel, stingy
    
    Middle Irish
    
    Irish dúr hard, tough, difficult, grim, dense, sluggish
    
    Scottish Gaelic dùr obstinate, stubborn, sullen, dour
    
    Scots dour
    
    English dour
    
    Latin dūrāre to harden, to last, to endure
    
    Latin indūrāre to harden, to endure
    
    Central Romance
    
    Italian indurare
    
    Eastern Romance
    
    Romanian îndura
    
    Western Romance
    
    Old French endurer / andurer to last for
    
    Middle French endurer
    
    French endurer
    
    Middle English enduren to last
    
    English endure
    
    Old French endurance
    
    Middle French endurance
    
    French endurance
    
    English endurance
    
    Spanish endurar
    
    Central Romance
    
    Italian durare
    
    Western Romance
    
    Old French durer to last for
    
    Middle French durer
    
    French durer
    
    Middle French duree duration, length
    
    French durée duration
    
    Middle English duren to last
    
    Spanish durar
    
    Albanian duroj
    
    Latin dūrātiō
    
    Central Romance
    
    Italian durazione
    
    Western Romance
    
    Old French duracion
    
    English duration
    
    Spanish duración
    
    Latin dūrābilis durable, lasting
    
    Central Romance
    
    Italian durabile
    
    Western Romance
    
    Old French durable
    
    Middle English durable
    
    English durable
    
    Latin dūritia hardness, rigidity, a harsh flavor, austerity, severity
    
    Central Romance
    
    Italian durezza harshness, rigidity, severity
    
    Western Romance
    
    Old French durece
    
    Middle English duresse
    
    English duress
    
    Spanish dureza hardness, arduousness
- Proto-Indo-European *drumós
  - Old Armenian տրամ tram solid, firm
    
    Middle Armenian տրամ tram solid ground
    
    Georgian ტრამა ṭrama wasteland
  - Germanic *trumaz firm, strong
    
    North Germanic
    
    Old Norse Þrymr
    
    West Germanic *trum
    
    Old English trum
    
    Middle English trum
    
    English trim
    
    Germanic *trumjaną to strengthen, to make fast
    
    West Germanic *trummjan
    
    Old English trymman to strengthen
    
    Middle English trymen / trimen
    
    English trim
- Proto-Indo-European *drutós
  - Balto-Slavic
    
    Baltic
    
    East Baltic
    
    Lithuanian drūtas firm, strong ^[3]
  - Celtic *drūtos
    
    Brythonic *drʉd
    
    Breton druz fat, fertile
    
    Cornish drudh favorite, cherished
    
    Middle Welsh drut
    
    Welsh drud expensive, daring
    
    Gaulish *drudos strong, vigorous
    
    French dru thick, luxurious (of hair), heavily
- Proto-Indo-European *drewō a firmness?
  - Germanic *trewwō fidelity, pledge
    
    East Germanic
    
    Gothic 𐍄𐍂𐌹𐌲𐌲𐍅𐌰 triggwa
    
    Medieval Latin tregua
    
    Italian tregua truce, rest, respite
    
    Spanish tregua truce, rest, break
    
    English treague
    
    North Germanic
    
    Old Norse trú
    
    Old Norse vantrú disbelief, lack of confidence
    
    Old East Norse
    
    Danish vantro disbelief
    
    West Germanic *treuwu
    
    Old English trēow truth, fidelity
    
    Middle English trewe / trewes
    
    English true noun
    
    English truce
    
    Frankish *treuwa
    
    Dutch trouw loyalty, faithfulness, marriage
    
    Old French trieve
    
    French trêve truce, break, rest
    
    Old High German triuwa
    
    German Treue faithfulness, loyalty
    
    Old Saxon triuwa / treuwe
    
    Old Norse trú
    
    Old Norse vantrú disbelief, lack of confidence
    
    Old East Norse
    
    Danish vantro disbelief
    
    Middle Low German truwe / trouwe
    
    Low German Treue
- Proto-Indo-European *drowstōs
  - Germanic *traustaz firm, strong
    
    Germanic *traustą shelter, aid, trust, confidence, alliance
    
    East Germanic
    
    Gothic 𐍄𐍂𐌰𐌿𐍃𐍄𐌹 trausti covenant, pact
    
    North Germanic
    
    Old Norse traust
    
    Danish trøst comfort, solace
    
    Icelandic traust trust, faith, confidence
    
    Old English
    
    English trust
    
    French trust a trust (group)
    
    Vietnamese tơ-rớt a trust (group)
    
    West Germanic
    
    Old English *trēast
    
    Middle English tryst / trist
    
    English tryst
    
    Frankish *traust
    
    Dutch troost comfort, consolation
    
    Old High German trōst
    
    German Trost consolation
    
    Germanic *traustijaną to make strong, to comfort
    
    North Germanic
    
    Old Norse treysta
    
    Old French
    
    Middle English tryst / trist
    
    English tryst
- Proto-Indo-European *dóru tree
  - Anatolian *dōru
    
    Hittite 𒋫𒀀𒊒 tāru wood, tree
    
    Hieroglyphic Luwian tarud- statue
    
    Indo-Iranian *taru
    
    Indo-Aryan
    
    Sanskrit 𑀢𑀭𑀼 taru tree
    
    Telugu తరువు taruvu tree
    
    Iranian
    
    Scythian *tūlyā tree
    
    Alanian *tul
    
    Alanian *tulʒæ diminutive
    
    Ossetian толдзӕ / тулдз tolʒæ tulʒ oak
    
    Hungarian tölgy oak
    
    Old Armenian
    
    Armenian թխկի tʻxki maple
    
    Ingush дийхк diı̇xk pine tree
    
    Saka *tūilā
    
    Khotani 𑀢𑁆𑀢𑀻𑀮 ttīla tree, shrub
  - Hellenic *dóru tree
    
    Classical Greek δόρῠ dóru wood, tree, pole, spear, lance
    
    Greek δόρυ dóry pike, spear
    
    English dory
    
    Hellenic *drutómoi tree cutters
    
    Mycenaean Greek 𐀉𐀬𐀵𐀗 du-ru-to-mo tree cutters
    
    Hellenic *der-drewom?
    
    Classical Greek δένδρον déndron tree
    
    Classical Greek ῥοδόδενδρον rhodódendron rosebay, oleander
    
    Latin rhododendron rosebay, oleander
    
    Translingual Rhododendron
    
    Vulgar Latin *arodandrum
    
    Vulgar Latin *lorandrum
    
    Central Romance
    
    Italian oleandro oleander
    
    Western Romance
    
    French oléandre
    
    English oleander
    
    Galician loendro oleander
    
    English dendr- / dendro-
    
    English dendrogram
  - Indo-Iranian *dā́ru tree, wood
    
    Indo-Aryan *dā́ru
    
    Sanskrit 𑀤𑀸𑀭𑀼 dā́ru wood, timber
    
    Sanskrit 𑀟𑀸𑀮 ḍāla branch ^[4]
    
    Hindi डाल ḍāl branch
    
    Iranian *dā́ru wood, tree
    
    Avestan dāuru wood
    
    Western Iranian
    
    Northwestern Iranian
    
    Kurdish دار dār tree, wood, staff
    
    Old Persian 𐎭𐎠𐎽𐎢𐎺 d-a-ru-u-v wood
    
    Persian دار dâr tree, wood, gallows
    
    Iranian *dā́rukah wood, tree, stick
    
    Sogdo-Bactrian
    
    Sogdian δārukā wood, stick
    
    Pashto لرګی largáy wood
    
    Western Iranian
    
    Northwestern Iranian
    
    Medean *dāruwkah
    
    Akkadian 𒁕𒊒𒊌𒆪 Da-ru-uk-ku place name
  - Tocharian *or
    
    Arshian or wood
    
    Kushean or wood
    
    Kushean ārwa firewood
  - Proto-Indo-European *dréwom
    
    Germanic *trewą
    
    East Germanic
    
    Gothic 𐍄𐍂𐌹𐌿 triu tree, wood, stick
    
    North Germanic
    
    Old Norse tré tree, mast, beam
    
    Danish træ tree, wood, timber
    
    Icelandic tré tree, wood
    
    West Germanic *treu
    
    Old English trēow tree
    
    Middle English treo / tre / trau
    
    English tree
    
    Frankish *treo
    
    Middle Dutch
    
    Dutch teer rare, boom is more common
  - Proto-Indo-European *derwóm
    
    Balto-Slavic *derwa
    
    Celtic *derwo-
    
    Brythonic
    
    Brythonic *Deruentiū hydronym: of the Oaks?, Water-?
    
    Old Welsh Derwennydd
    
    Latin Derventiō
    
    Old English Derwent
    
    Old Norse *Djúrabýr
    
    Old English Deoraby (Danelaw) Derby
    
    English Derby ^[5]
    
    English derby ^[5]
    
    Old English Derƿentby Derby lit. "Derwent-town"
    
    English Derby ^[5]
    
    English derby ^[5]
    
    English Derwent
    
    Welsh derw oaks
    
    Old Irish derb wooden bucket
    
    Old Irish derb sure, certain, fixed, truly
    
    Old Irish derbráthair full brother, brother german
    
    Irish deartháir brother
    
    Old Irish derbṡiur sister
    
    Irish deirfiúr sister
    
    Irish dearbh sure, certain
    
    Gaulish *deruo-
    
    Latin Dereventum place name (in Gallia Lugdunensis)
    
    Western Romance
    
    French Drevant
    
    Latin Dervus
    
    French Der
    
    French Montier-en-Der
    
    Old French dervée oaken
    
    Germanic *terwą tar, resin
    
    North Germanic
    
    Old Norse tjara
    
    Danish tjære tar
    
    Icelandic tjara tar
    
    Finnic *tërva
    
    Finnish terva tar
    
    Samic *tërvē
    
    Northern Sámi darvi tar
    
    West Germanic
    
    Old English teru tar, resin
    
    English tar
    
    Frankish
    
    Dutch teer tar
    
    Old Saxon
    
    Low German
    
    German Teer tar
  - Proto-Indo-European *drwós *drwh₂ós collective
    
    Albanian dru tree, wood
    
    Balto-Slavic
    
    East Baltic
    
    Finnic *tërva
    
    Finnish terva tar
    
    Samic *tërvē
    
    Northern Sámi darvi tar
    
    Lithuanian dervà tar, resin, wood chips
    
    Slavic *drъvo wood
    
    East Slavic
    
    Russian дрова drova firewood
    
    South Slavic
    
    Old Church Slavonic дръва drŭva wood
    
    Serbo-Croatian дрво drvo tree, wood, timber
    
    West Slavic
    
    Polish drwa
    
    Polish drwal lumberjack
    
    Celtic *daru tree, oak
    
    Brythonic *dar oak, tree
    
    Welsh dâr oak tree
    
    Brythonic *aβaldar apple tree
    
    Old English apuldor apple tree partial translation
    
    English Appledore
    
    Gaulish
    
    Classical Greek λάριξ lárix larch, Venice turpentine
    
    Latin larix larch
    
    Translingual Larix taxonomic genus of conifers, the larches
    
    Italian larice larch
    
    Old High German larihha
    
    German Lärche larch
    
    Dutch lork larch
    
    English larch larch
    
    Finnic
    
    Estonian lehis larch
    
    Finnish lehtikuusi larch lit. "larch-spruce"
    
    Old Irish dair oak
    
    Old Irish Cell Dara place name: Church of the Oak, Kildare
    
    Irish Cill Dara
    
    English Kildare
    
    Irish dair oak
    
    Celtic *dru-wits *druwits druid
    
    Brythonic *drüw
    
    Welsh dryw druid, seer
    
    Old English drȳ sorcerer, magician
    
    Gaulish *druwits
    
    Gaulish *druwides druids, the Druids
    
    Classical Greek δρυΐδαι druḯdai the Druids
    
    Latin Druidae the Druids
    
    French druide druid
    
    English druid
    
    Mandarin 德魯伊 délǔyī druid
    
    Italian druida druid
    
    Spanish druida druid
    
    Old Irish druí / druï druid, sorcerer
    
    Middle Irish
    
    Irish draoi druid, sorcerer, diviner, trickster
    
    Irish draíodóir magician
    
    Scottish Gaelic draoidh druid, sorcerer, philosopher
    
    Old Irish druídecht / draídecht druidry, wizardry, occult science
    
    Middle Irish
    
    Irish draíocht druidry, witchfraft, magic, enchantment
    
    Manx druaight charm, spell, druid
    
    Scottish Gaelic draoidheachd bewitchment, sorcery, druidry, magic, charm, enchantment
    
    Hellenic
    
    Classical Greek δρῦς drûs tree, timber, oak
    
    Classical Greek δρυοκολάπτης druokoláptis woodpecker
    
    Greek δρυοκολάπτης dryokoláptis woodpecker
    
    Classical Greek χαμαίδρυς / χαμαίδρῡς khamaídrus khamaídrūs wall germander "ground-oak"
    
    Latin chamaedrys
    
    French germandrée
    
    English germander
    
    German Gamander
    
    Italian camedrio avens
    
    Classical Greek Δρυάς Druás tree nymph, dryad oblique stem Δρυάδ- Druád-
    
    Latin Dryas dryad, druidess oblique stem Dryad-
    
    French dryade dryad
    
    English dryad
    
    Indo-Iranian
    
    Indo-Aryan
    
    Sanskrit द्रु drú wood, wooden implement, branch
    
    Sanskrit द्रुपद drupadá post, (wooden) pillar
    
    Messapic *daras oaks
    
    Classical Greek Τάρας Táras Tarentum Greek colony in southern Italy
    
    Latin Tarentum
    
    Central Romance
    
    Italian Tarento
    
    Italian Tarantino
    
    Italian tarantola tarantula
    
    English tarantula
  - Proto-Indo-European *drumós
    
    Germanic *trumaz root
    
    West Germanic
    
    Old English trum root, (tree) stump
    
    Old English wyrttrum
    
    Old English wyrttrumian to grow upward, as from a root or seed
    
    Hellenic
    
    Classical Greek δρυμός drumós copse, thicket, wood
    
    Classical Greek Δρυμός Drumós place name: Thicket
    
    Latin Drymus
    
    Classical Greek Δρυμαία Drumaia
    
    Indo-Iranian
    
    Indo-Aryan
    
    Sanskrit द्रुम druma tree
  - Proto-Indo-European *drukós wooden
    
    Old Armenian տարգալ targal (wooden) spoon
    
    Armenian գդալ gdal spoon
    
    Celtic
    
    Old Irish
    
    Middle Irish drochta wooden basin, trough
    
    Germanic *trugaz trough
    
    North Germanic
    
    Old Norse trog
    
    Icelandic trog trough
    
    West Germanic
    
    Old English trog trough
    
    English trough
    
    Irish trach trough
    
    Frankish *trog
    
    Dutch trog trough, trench
    
    Old High German troc
    
    German Trog trough, trench
    
    Italian trogolo trough
  - Proto-Indo-European *dréwh₂nom *dréwh₂tom *dréwh₂yom wooden implement
    
    Anatolian
    
    Hittite taru̯āli pestle?
    
    Old Armenian տոռն toṙn (wooden) pestle
    
    Germanic *trawją
    
    North Germanic
    
    Old Norse treyja
    
    Old Swedish trø
    
    West Germanic
    
    Old English trēġ wooden serving board, tray
    
    English tray
    
    Old Saxon
    
    Low German Treechel trough
    
    Hellenic
    
    Classical Greek δρουίτη drouítē (wooden) tub
    
    Indo-Iranian *dráwnam
    
    Indo-Aryan *dráwnam
    
    Sanskrit द्रोण dróṇa wooden bucket, trough
    
    Magadhi
    
    Bengali ডিঙ্গা dinga small fishing boat, canoe
    
    English dinghy
  - Proto-Indo-European
    
    Indo-Iranian
    
    Indo-Aryan
    
    Sanskrit dārv wooden
    
    Sanskrit दर्वि dárvi spoon, ladle
- Proto-Indo-European *dweh₂- long?, distant?, enduring? or related to *dyew-: "day"?
  - Hellenic
    
    Classical Greek δήν dḗn for a long time, long ago
    
    Italic
    
    Latin dēmum at last, only
  - Proto-Indo-European *duh₂rós
    
    Italic *dūros
    
    Latin durus hard, harsh, vigorous, stern, unyielding ^[3]
    
    Latin duracinus hard-berried, stone fruit
    
    Central Romance
    
    Dalmatian drucno
    
    Italian duracina
    
    Western Romance
    
    Old French duraine
    
    Spanish durazno peach Latin American only
    
    Quechua turasnu peach
    
    French duracine type of peach
    
    Classical Greek δωράκινον dōrákinon type of peach
    
    Greek ροδάκινο rodákino peach
    
    Classical Syriac ܕܘܪܩܝܢܐ dōraqqīnā apricot, peach
    
    Arabic دُرَّاق durrāq peach
    
    Central Romance
    
    Italian duro hard, tough, harsh
    
    Insular Romance
    
    Sardinian duru hard, tough
    
    Western Romance
    
    Old French
    
    Middle French
    
    French dur hard, tough, harsh
    
    Spanish duro hard, solid, tough, cruel, stingy
    
    Middle Irish
    
    Irish dúr hard, tough, difficult, grim, dense, sluggish
    
    Scottish Gaelic dùr obstinate, stubborn, sullen, dour
    
    Scots dour
    
    English dour
    
    Latin dūrāre to harden, to last, to endure
    
    Latin indūrāre to harden, to endure
    
    Central Romance
    
    Italian indurare
    
    Eastern Romance
    
    Romanian îndura
    
    Western Romance
    
    Old French endurer / andurer to last for
    
    Middle French endurer
    
    French endurer
    
    Middle English enduren to last
    
    English endure
    
    Old French endurance
    
    Middle French endurance
    
    French endurance
    
    English endurance
    
    Spanish endurar
    
    Central Romance
    
    Italian durare
    
    Western Romance
    
    Old French durer to last for
    
    Middle French durer
    
    French durer
    
    Middle French duree duration, length
    
    French durée duration
    
    Middle English duren to last
    
    Spanish durar
    
    Albanian duroj
    
    Latin dūrātiō
    
    Central Romance
    
    Italian durazione
    
    Western Romance
    
    Old French duracion
    
    English duration
    
    Spanish duración
    
    Latin dūrābilis durable, lasting
    
    Central Romance
    
    Italian durabile
    
    Western Romance
    
    Old French durable
    
    Middle English durable
    
    English durable
    
    Latin dūritia hardness, rigidity, a harsh flavor, austerity, severity
    
    Central Romance
    
    Italian durezza harshness, rigidity, severity
    
    Western Romance
    
    Old French durece
    
    Middle English duresse
    
    English duress
    
    Spanish dureza hardness, arduousness
    
    Old Armenian երկար erkar long, extended, slow ^[6]
    
    Armenian երկար erkar long, lengthy, protacted
    
    Hellenic *dwārós alternate zero-grade stem where *h₂ instead of *w is vocalized
    
    Classical Greek δηρός dērós long, too long
    
    Indo-Iranian *duHrás long, far
    
    Indo-Aryan *duHrás
    
    Sanskrit दूर dūrá
    
    Pali dūra
    
    Sauraseni 𑀤𑀽𑀭 dūra
    
    Hindustani
    
    Hindi दूर dūr distant, far, away from, off
    
    Northwestern Sauraseni
    
    Kashmiri دوٗر dūr
    
    Punjabi ਦੂਰ dūr far
    
    Western Sauraseni
    
    Romani dur far
    
    Telugu దూరము dūramu distance
    
    Iranian *duHráh
    
    Avestan dūrāt̰ from afar
    
    Western Iranian
    
    Northwestern Iranian
    
    Kurdish دوور dûr distant, far off
    
    Old Persian
    
    Middle Persian
    
    Persian دور dūr far, distant, away

Visual

Collected English words

Rhododendron, oleander, trow, true, truth, troth, betroth, betrothal, dour, endure, endurance, duration, durable, duress, trim, trim, treague, true, truce, trust, tryst, dory, dendr-, tree, Derwent, Derby, derby, tar, Appledore, Larix, larch, Kildare, dryad, germander, tarantula, trough, tray, dinghy, druid, dendrogram

Footnotes

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It is impossible to tell at this point if the original meaning was "tree" or "firm". Compare Latin robustus/robur.
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PIE *drewéyeti and Germanic *trewwaną are implied by the form of the Germanic adjective *triwwiz. Compare for example Germanic *hriwwiz: "regretful" from Germanic *hrewwaną: "to regret, to rue", from PIE *krewéyti: "cause to break". But I know of no other trace of *drewéyeti or *trewwaną, besides those through *triwwiz. Indeed, Germanic then re-derives a verb from the *triwwiz to get *triwwijaną.
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In my opinion, Latin dūrus is probably a mix of *druwós: "firm" (with metathesis) and *duh₂rós: "long" (with metaphor to time, also present in Armenian and Greek).

In Indo-Iranian *duh₂rós is (nearly) always a long distance, not a long time. There is another adjective very similar to Latin dūrus, *dʰruwás: "firm, fixed, strong" (Sanskrit dhruvá), but the *dʰ means it is not formally equivalent for Latin durus and English true, but to Latin firmus=lat-Latn and English darn`=ng-Latn (as in socks).

Since Balto-Slavic merges *d and *dʰ, Lithuanian drūtas: "firm, strong" could be from either group (or both!)
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I don't have any sources for an etymology for Sanskrit डाल ḍāla: "branch". But since in early Sanskrit d and ḍ are in conditioned alternation, and r and l are in dialectic alternation, it makes sense to tentatively connect it to दारु dā́ru: "wood, timber".
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English Derby is a confluence of related influences: 1) organic formation of Derwent-by: "Derwent-town, town on the River Derwent", 2) from the Roman settlement Derventio (later Derbentio), itself from the Brythonic name of the river Derwent, 3) Old Norse Djúrabý, the Danelaw name of the town, literally "Deer-town", but probably influenced by the sound of one or both of the other two.

English derby: "a race", is after the Earls of Derby, several of whom were famous patrons of horse-racing, especially Edward Smith-Stanley, 12th Earl of Derby who organized a sweepstake horse race in 1779 which was the founding event of two of the five most prestigious horse races in England: the Derby, open to colts and fillies, and the Oaks, restricted to fillies. Either of which counts as the second leg in the original "Triple Crown".

Nota bene, Oaks after the London estate of the Earls of Derby (now Oaks Park), which connects back to the original Brythonic name *Deruentiū: "of the Oaks", such that these two equivalent races, Derby and Oaks, are ultimately synonymous.
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Yes, Armenian erkar really is cognate to Greek dērós! Compare Armenian erku: vs. Greek dúo, both "two".

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