Online Etymology Dictionary

traumatise (v.): chiefly British English spelling of traumatize; for suffix, see -ize. Related: Traumatised; traumatising.
traumatize (v.): 1893, in reference to physical wounds; 1949 in the psychological sense, from Greek traumat-, stem of trauma (see trauma).
travail (n.): "labor, toil," mid-13c., from Old French travail "work, labor, toil, suffering or painful effort, trouble; arduous journey" (12c.), from travailler "to toil, labor," originally "to trouble, torture, torment," from Vulgar Latin *tripaliare "to torture," from *tripalium (in Late Latin trepalium) "instrument of torture," probably from Latin tripalis "having three stakes" (from tria "three;" see three + palus "stake;" see pale (n.)), which sounds ominous, but the exact notion is obscure. The verb is recorded from late 13c. in English, from the verb in Old French.
trave (n.): late 14c., from Old French traf "crossbeam," from Latin trabem (nominative trabs) "beam," from PIE *treb- "dwelling" (see tavern).
travel (v.): late 14c., "to journey," from travailen (1300) "to make a journey," originally "to toil, labor" (see travail). The semantic development may have been via the notion of "go on a difficult journey," but it also may reflect the difficulty of any journey in the Middle Ages. Replaced Old English faran. Related: Traveled; traveling. Traveled (adj.) "having made journeys, experienced in travel" is from early 15c. Traveling salesman is attested from 1885.
travel (n.): late 14c., "action of travelling," from travel (v.). Travels "accounts of journeys" is recorded from 1590s. Travel-agent is from 1925.
traveler (n.): also traveller, late 14c., agent noun from travel (v.). Traveler's check is from 1891.
travelogue (n.): "a talk on travel," 1903, a hybrid word coined by U.S. traveler Burton Holmes (1870-1958) from travel + Greek-derived -logue, abstracted from monologue.
traverse (v.): early 14c., "pass across, over, or through," from Old French traverser "to cross, place across" (11c.), from Vulgar Latin *traversare, from Latin transversare "to cross, throw across," from Latin transversus "turn across" (see transverse). As an adjective from early 15c. Related: Traversed; traversing.
traverse (n.): "act of passing through a gate, crossing a bridge, etc.," mid-14c., from Old French travers, from traverser (see traverse (v.)). Meaning "a passage by which one may traverse" is recorded from 1670s. Military fortification sense of "barrier, barricade" is recorded from 1590s.
travertine (n.): 1797, from Italian travertino "a kind of building stone," from Latin tiburtinus, from Tiburs, adjective from Tibur (modern Tivoli), in Latium.
travesty (n.): 1670s, "literary burlesque of a serious work," from adjective meaning "dressed so as to be made ridiculous, parodied, burlesqued" (1660s), from French travesti "dressed in disguise," past participle of travestir "to disguise" (1590s), from Italian travestire "to disguise," from Latin trans- "over" (see trans-) + vestire "to clothe" (see wear (v.)).
Traviata, La: title of an opera by Verdi, Italian, literally "the woman led astray," from traviata literally "to lead beyond the way," from tra- "across, beyond" (from Latin trans-; see trans-) + via "way" (see via).
Travis: masc. proper name, also a surname (late 12c.), from an Old French word meaning "to cross over," related to traverse (v.). Probably a name for a gatekeeper or the toll collector of a bridge.
travois (n.): type of American Indian transport, 1847, said to be ultimately from a Canadian Indian pronunciation of travail.
trawl (v.): 1560s, from Dutch tragelen, from Middle Dutch traghelen "to drag," from traghel "dragnet," probably from Latin tragula "dragnet." Related: Trawled; trawling.
trawler (n.): 1590s, agent noun from trawl.
tray (n.): Old English treg, trig "flat wooden board with a low rim," from Proto-Germanic *traujam (source also of Old Swedish tro, a corn measure), from PIE *drou-, variant of *deru-, forming words refering to objects made of wood (see tree (n.)). The primary sense may have been "wooden vessel."
treacherous (adj.): early 14c., from Old French trecheros, tricheros "deceitful" (12c.), from trecheor, tricheor "cheat, deceiver, liar, impostor, trickster," agent noun from trechier, trichier "to cheat, trick" (see trick (n.)). Figuratively, of things, from c. 1600. Related: Treacherously; treacherousness. Middle English had treacher "deceiver, cheat, traitor."
treachery (n.): "treasonable or perfidious conduct," c. 1200, from Old French trecherie, tricherie "deceit, cheating, trickery, lies" (12c.), from trechier "to cheat, deceive" (see trick (n.)).
treacle (n.): mid-14c., "medicinal compound, antidote for poison," from Old French triacle "antidote, cure for snake-bite" (c. 1200), from Vulgar Latin *triacula, from Latin theriaca, from Greek theriake (antidotos) "antidote for poisonous wild animals," from fem. of theriakos "of a wild animal," from therion "wild animal," diminutive of ther (genitive theros) "wild animal," from PIE root *ghwer- "wild" (see fierce).

Sense of "molasses" is first recorded 1690s (the connection may be from the use of molasses as a laxative, or its use to disguise the bad taste of medicine); that of "anything too sweet or sentimental" is from 1771. Related: Treacly.
tread (v.): Old English tredan "to tread, step on, trample; traverse, pass over" (class V strong verb; past tense træd, past participle treden), from Proto-Germanic *tred- (source also of Old Saxon tredan, Old Frisian treda, Middle Dutch treden, Old High German tretan, German treten, Gothic trudan, Old Norse troða), from PIE *der- (1) "assumed base of roots meaning 'to run, walk, step'" [Watkins]. Related: Trod; treading.
tread (n.): early 13c., "a step or stepping, pressure with the foot," from tread (v.); in reference to automobile tires, it is recorded from 1906.
treadle (n.): "lever worked by foot," c. 1400, from Old English tredel "step, stair, sole of the foot," from tredan "to tread" (see tread (v.)) + instrumental suffix -el (1). Compare handle (n.).
treadmill (n.): invented (and named) 1822; originally an instrument of prison discipline; from tread (v.) + mill (n.1). Treadwheel as a similar method of driving machinery is from 1570s.
As a corrective punishment, the discipline of the stepping mill has had a most salutary effect upon the prisoners, and is not likely to be easily forgotten, while it is an occupation which by no means interferes with, nor is calculated to lessen the value of, those branches of prison regulation which provide for the moral and religious improvement of the criminal. ["Description of the Tread Mill Invented by Mr. William Cubitt of Ipswich for the Employment of Prisoners," London, 1822]
By later generations regarded as a path to physical fitness.
treason (n.): c. 1200, "betraying; betrayal of trust; breech of faith," from Anglo-French treson, from Old French traison "treason, treachery" (11c.; Modern French trahison), from Latin traditionem (nominative traditio) "a handing over, delivery, surrender" (see tradition). Old French form influenced by the verb trair "betray." In old English law, high treason is violation by a subject of his allegiance to his sovereign or to the state; distinguished from petit treason, treason against a subject, such as murder of a master by his servant. Constructive treason was a judicial fiction whereby actions carried out without treasonable intent, but found to have the effect of treason, were punished as though they were treason itself. The protection against this accounts for the careful wording of the definition of treason in the U.S. Constitution.
treasonable (adj.): "of or pertaining to treason," late 14c., from treason + -able. Related: Treasonably.
treasonous (adj.): mid-15c., from treason + -ous. Related: Treasonously.
treasure (n.): mid-12c., tresor, from Old French tresor "treasury, hoard, treasure" (11c., Modern French trésor), from Gallo-Roman *tresaurus, from Latin thesaurus "treasury, treasure" (source also of Spanish, Italian tesoro), from Greek thesauros "store, treasure, treasure house" (see thesaurus). In Middle English also thresur, etc.; modern spelling is from 16c. Replaced Old English goldhord. General sense of "anything valued" is recorded from c. 1200. Treasure hunt is first recorded 1913. For treasure trove, see trove.
treasure (v.): late 14c., "to amass treasure; to store up for the future," also figurative, "regard as precious, retain carefully in the mind," from treasure (n.). Related: Treasured; treasuring.
treasurer (n.): late 13c., from Old North French, Anglo-French tresorer, Old French tresorier, from tresor (see treasure (n.)). Treasury bill attested from 1797.
treasury (n.): c. 1300, "room for treasure," from Old French tresorie "treasury" (11c.), from tresor (see treasure (n.)). Meaning "department of state that controls public revenue" is recorded from late 14c. An Old English word for "room for treasure" was maðm-hus and for "treasury," feo-hus (see fee).
treat (v.): c. 1300, "negotiate, bargain, deal with," from Old French traitier "deal with, act toward; set forth (in speech or writing)" (12c.), from Latin tractare "manage, handle, deal with, conduct oneself toward," originally "drag about, tug, haul, pull violently," frequentative of trahere (past participle tractus) "to pull, draw" (see tract (n.1)).

Meaning "to entertain with food and drink without expense to the recipient by way of compliment or kindness (or bribery)" is recorded from c. 1500. Sense of "deal with, handle, or develop in speech or writing" (early 14c.) led to the use in medicine "to attempt to heal or cure, to manage in the application of remedies" (1781). Related: Treated; treating.
treat (n.): late 14c., "action of discussing terms," from treat (v.). Sense of "a treating with food and drink, an entertainment given as a compliment or expression of regard" (1650s) was extended by 1770 to "anything that affords much pleasure."
treatable (adj.): c. 1300, "amenable to reason," from Anglo-French tretable, Old French traitable, and in part from treat (v.) + -able. Of wounds, diseases, etc., "receptive to treatment," early 15c.
treatise (n.): early 14c., from Anglo-French tretiz (mid-13c.), contracted from Old French traitis "treatise, account," from traitier "deal with; set forth in speech or writing" (see treat (v.)).
treatment (n.): 1560s, "conduct or behavior toward someone or something," from treat (v.) + -ment. In the medical sense, it is first recorded 1744.
treaty (n.): late 14c., "treatment, discussion," from Anglo-French treté, Old French traitié "assembly, agreement, dealings," from Latin tractatus "discussion, handling, management," from tractare "to handle, manage" (see treat (v.)). Sense of "contract or league between nations or sovereigns" is first recorded early 15c.
treble (adj.): "three times, triple," c. 1300, from Old French treble (12c.), from Latin triplus "threefold" (see triple). Related: Trebly.
treble (v.): "to multiply by three," early 14c., from Old French trebler, from treble "triple" (see treble (adj.)). Related: Trebled; trebling.
treble (n.): "highest part in music, soprano," mid-14c., from Anglo-French treble, Old French treble "a third part," noun use of adjective (see treble (adj.)). In early contrapuntal music, the chief melody was in the tenor, and the treble was the "third" part above it (after the alto).
trebuchet (n.): "medieval stone-throwing engine of war," c. 1300 (in Anglo-Latin from early 13c.), from Old French trebuchet (12c.) "stone-throwing siege engine," from trabuchier "to overturn, fall to the ground, overthrow" (11c.), from tra- (from Latin trans-, here expressing "displacement") + Old French buc "trunk, bulk," from Frankish *buk- "trunk of the body," from Proto-Germanic *bheu-, variant of *beu-, used in forming words loosely associated with swelling (such as German bauch "belly;" see bull (n.2)).
tree (n.): Old English treo, treow "tree" (also "timber, wood, beam, log, stake"), from Proto-Germanic *treuwaz- (source also of Old Frisian tre, Old Saxon trio, Old Norse tre, Gothic triu "tree"), from PIE *drew-o-, from *deru- "oak" (source also of Sanskrit dru "tree, wood," daru "wood, log;" Greek drys "oak," drymos "copse, thicket," doru "beam, shaft of a spear;" Old Church Slavonic drievo "tree, wood;" Serbian drvo "tree," drva "wood;" Russian drevo "tree, wood;" Czech drva; Polish drwa "wood;" Lithuanian derva "pine, wood;" Old Irish daur, Welsh derwen "oak," Albanian drusk "oak"). This is from PIE *drew-o-, a suffixed form of the root *deru- "to be firm, solid, steadfast" (see true), with specialized sense "wood, tree" and derivatives referring to objects made of wood.
The line which divides trees from shrubs is largely arbitrary, and dependent upon habit rather than size, the tree having a single trunk usually unbranched for some distance above the ground, while a shrub has usually several stems from the same root and each without a proper trunk. [Century Dictionary]
The widespread use of words originally meaning "oak" in the sense "tree" probably reflects the importance of the oak to ancient Indo-Europeans. In Old English and Middle English also "thing made of wood," especially the cross of the Crucifixion and a gallows (such as Tyburn tree, famous gallows outside London). Middle English also had plural treen, adjective treen (Old English treowen "of a tree, wooden"). For Dutch boom, German Baum, the usual words for "tree," see beam (n.). Meaning "framework of a saddle" is from 1530s. Meaning "representation of familial relationships in the form of a tree" is from c. 1300. Tree-hugger, contemptuous for "environmentalist" is attested by 1989.
Minc'd Pyes do not grow upon every tree,
But search the Ovens for them, and there they be.
["Poor Robin," Almanack, 1669]
tree (v.): "to chase up a tree," 1700, from tree (n.). Meaning "take a tree-like form" is from 1884. Related: Treed; treeing.
tree-frog (n.): 1738, from tree (n.) + frog (n.1).
tree-house (n.): 1867, from tree (n.) + house (n.).
tree-top (n.): 1520s, from tree (n.) + top (n.).
treeless (adj.): 1742, from tree (n.) + -less.
tref (n.): Welsh, literally "hamlet, home, town," from PIE *treb- "dwelling" (see tavern).
trefoil (n.): late 14c., type of clover, from Anglo-French trifoil (13c.), Old French trefueil "clover, clover-leaf," from Latin trifolium "three-leaved plant," from tri- "three" (see tri-) + folium "leaf" (see folio). As a type of ornamental figure in medieval architecture, early 15c.