Online Etymology Dictionary

toxemia (n.): "blood-poisoning," also toxaemia, 1848, from toxo- (before vowels tox-, comb. form of Greek toxon (see toxic)) + Greek haima "blood" (see -emia).
toxic (adj.): 1660s, from French toxique and directly from Late Latin toxicus "poisoned," from Latin toxicum "poison," from Greek toxikon (pharmakon) "(poison) for use on arrows," from toxikon, neuter of toxikos "pertaining to arrows or archery," and thus to a bow, from toxon "bow," probably from a Scythian word that also was borrowed into Latin as taxus "yew." Watkins suggests a possible source in Iranian taxša- "bow," from PIE *tekw- "to run, flee." As a noun from 1890.
toxicity (n.): "state of being toxic," 1880, from toxic + -ity.
toxicology (n.): 1815, from French toxicologie (1812), from comb. form of Greek toxikon "arrow poison" (see toxic) + -logia (see -logy). Related: Toxicological; toxicologist.
toxin (n.): "organic poison," especially one produced by bacteria in an animal body, 1886, from toxic + -in (2).
toxoplasmosis (n.): 1977, from toxoplasma (1926), coined 1909 in French from toxo-, comb. form of Greek toxon (see toxic) + plasma (see plasma) + -osis.
toy (n.): c. 1300, "amorous playing, sport," later "piece of fun or entertainment" (c. 1500), "thing of little value, trifle" (1520s), and "thing for a child to play with" (1580s). Of uncertain origin, and there may be more than one word here. Compare Middle Dutch toy, Dutch tuig "tools, apparatus; stuff, trash," in speeltuig "play-toy, plaything;" German Zeug "stuff, matter, tools," Spielzeug "plaything, toy;" Danish tøi, Swedish tyg "stuff, gear." Applied as an adjective to things of diminutive size, especially dogs, from 1806. Toy-boy is from 1981.
toy (v.): "deal carelessly (with), trifle," 1520s, from toy (n.) in its older sense.
If he be merie and toy with any,
His wife will frowne, and words geve manye.
["Song of the Bachelor's Life," 16c.]
Related: Toyed; toying.
toy-box (n.): also toybox, 1819, from toy (n.) + box (n.).
Toyota: Japanese automaker, begun 1930s as a division of Toyoda Automatic Loom Works, named for the family name of the founder. There seems to be no one accepted explanation for the change from -d- to -t-.
trace (v.): late 14c., "follow (a course); draw a line, make an outline of something," also figurative; "ponder, investigate," from Old French tracier "look for, follow, pursue" (12c., Modern French tracer), from Vulgar Latin *tractiare "delineate, score, trace" (source also of Spanish trazar "to trace, devise, plan out," Italian tracciare "to follow by foot"), a frequentative form from Latin tractus "track, course," literally "a drawing out," from past participle stem of trahere "to pull, draw" (see tract (n.1)).

Meaning "move along, pass over" (a path, etc.) is attested from c. 1400; that of "track down, follow the trail of" is early 15c. Meaning "copy a drawing on a transparent sheet laid over it" is recorded from 1762. Related: Traced; tracing.
trace (n.2): "straps or chains by which an animal pulls a vehicle," c. 1300, from earlier collective plural trays, from Old French traiz, plural of trait "strap for harnessing, act of drawing," from Latin tractus "a drawing, track," from stem of trahere "to pull, draw" (see tract (n.1)). Related: Traces.
trace (n.1): "track made by passage of a person or thing," c. 1300, from Old French trace "mark, imprint, tracks" (12c.), back-formation from tracier (see trace (v.)). Scientific sense of "indication of minute presence in some chemical compound" is from 1827. Traces "vestiges" is from c. 1400.
traceable (adj.): 1748, from trace (v.) + -able. Related: Traceability.
tracer (n.): c. 1500, "one who tracks or searches," agent noun from verb form of trace (n.1). Meaning "bullet whose course is made visible" is from 1910.
tracery (n.): mid-15c., "a place for drawing," formed in English from trace (v.) + -ery. Architectural sense, in reference to intersecting rib work in the upper part of a gothic window, is attested from 1660s. "Introduced by Wren, who described it as a masons' term" [Weekley].
trachea (n.): late 14c., from Medieval Latin trachea (13c.), as in trachea arteria, from Late Latin trachia, from Greek trakheia, in trakheia arteria "windpipe," literally "rough artery" (so called from the rings of cartilage that form the trachea), from fem. of trakhys "rough," from PIE *dhre-gh-, suffixed form of root *dher- (1). See artery for connection with windpipe in Greek science. Related: Tracheal.
tracheostomy (n.): 1726, from tracheo-, used as a comb. form of trachea + -ostomy "artificial opening," from Modern Latin stoma "opening, orifice," from Greek stoma "mouth" (see stoma).
tracheotomy (n.): 1726, Modern Latin, coined 1718 by German surgeon Lorenz Heister (1683-1758); see trachea + -tomy.
trachoma (n.): disease of the eyes, 1690s, from Modern Latin trachoma, from Greek trakhoma "roughness," from trakhys "rough."
track (n.): late 15c., "footprint, mark left by anything," from Old French trac "track of horses, trace" (mid-15c.), possibly from a Germanic source (compare Middle Low German treck, Dutch trek "drawing, pulling;" see trek). Meaning "lines of rails for drawing trains" is from 1805. Meaning "branch of athletics involving a running track" is recorded from 1905. Meaning "single recorded item" is from 1904, originally in reference to phonograph records. Meaning "mark on skin from repeated drug injection" is first attested 1964.

Track record (1955) is a figurative use from racing, "performance history" of an individual car, runner, horse, etc. (1907, but the phrase was more common in sense "fastest speed recorded at a particular track"). To make tracks "move quickly" is American English colloquial first recorded 1835; to cover (one's) tracks in the figurative sense first attested 1898; to keep track of something is attested from 1883. American English wrong side of the tracks "bad part of town" is by 1901. Track lighting attested from 1970.
track (v.): "to follow or trace the footsteps of," 1560s, from track (n.). Meaning "leave a footprint trail in dirt, mud, etc." is from 1838. Of film and TV cameras, 1959. Related: Tracked; tracking.
tracker (n.): 1610s, agent noun from track (v.).
trackless (adj.): "pathless, untrodden," 1650s, from track (n.) + -less.
tract (n.1): "area," mid-15c., "period or lapse of time," from Latin tractus "track, course, space, duration," lit, "a drawing out or pulling," from stem of trahere "to pull, draw," from PIE root *tragh- "to draw, drag, move" (source also of Slovenian trag "trace, track," Middle Irish tragud "ebb;" perhaps with a variant form *dhragh-; see drag (v.)). The meaning "stretch of land or water" is first recorded 1550s. Specific U.S. sense of "plot of land for development" is recorded from 1912; tract housing attested from 1953.
tract (n.2): "little book, treatise" mid-12c., probably a shortened form of Latin tractatus "a handling, treatise, treatment," from tractare "to handle" (see treat (v.)). Related: Tractarian.
tractable (adj.): "manageable," early 15c., from Latin tractabilis "that may be touched or handled, workable, tangible, manageable," figuratively, "pliant," from tractare "to handle, manage" (see treat (v.)). Related: Tractability.
traction (n.): early 15c., "a drawing or pulling" (originally the pulling of a dislocated limb to reposition it), from Medieval Latin tractionem (nominative tractio) "a drawing" (mid-13c.), noun of action from past participle stem of Latin trahere "to pull, draw" (see tract (n.1)). Sense of "rolling friction of a vehicle" first appears 1825. In modern medical care, "a sustained pull to a part of the body to hold fractured bones in position," 1885.
tractor (n.): 1856, "something that pulls," from Modern Latin tractor "that which draws," agent noun from past participle stem of Latin trahere "to pull, draw" (see tract (n.1)). Earlier used of a quack device consisting of two metal rods which were supposed to relieve rheumatism (1798, in full Perkins's metallic tractor); still the main sense in Century Dictionary (1891).

Sense of "an engine or vehicle for pulling wagons or plows" is recorded by 1896, from earlier traction engine (1859). The meaning "powerful truck for pulling a freight trailer" is first found 1926; tractor-trailer as "combined motor-truck and trailer" is from 1914.
trad (adj.): 1956, slang shortening of traditional jazz. Its general slang use for "traditional" is recorded from 1963.
trade (n.): late 14c., "path, track, course of action," introduced by the Hanse merchants, from Middle Dutch or Middle Low German trade "track, course" (probably originally of a ship), cognate with Old English tredan (see tread (v.)).

Sense of "one's habitual business" (1540s) developed from the notion of "way, course, manner of life" (mid-15c.); sense of "buying and selling, exchange of commodities" is from 1550s. Meaning "act of trading" is from 1829. Trade-name is from 1821; trade-route is from 1873; trade-war is from 1899. Trade union is attested from 1831. Trade wind (1640s) has nothing to do with commerce, but preserves the obsolete sense of "in a habitual or regular course."
trade (v.): 1540s, "to tread a path," from trade (n.). Meaning "to occupy oneself (in something)" is recorded from c. 1600. Meaning "to barter" is by 1793. The U.S. sports team sense of "to exchange one player for another" is attested from 1899. Related: Traded; trading. To trade down is attested from 1942; trade up from 1959. Trade places "exchange situations" is from 1917. Trading post is recorded from 1796. Trading stamp, given by merchants and exchangeable for goods, is from 1897.
trade-in (n.): 1917, in reference to used cars, from verbal phrase, from trade (v.) + in (adv.).
trade-off (n.): also tradeoff, "sacrifice of one benefit for another," 1959, from verbal phrase to trade off; see trade (v.) + off (adv.).
trademark (n.): also trade-mark, 1838 (the thing itself attested continuously from 14c., apparently originally the watermarks on paper), from trade (n.) + mark (n.1). Figurative use by 1869. As a verb, from 1904. Related: Trademarked; trademarking.
trader (n.): "dealer, trafficker, one engaged in commerce," 1580s, agent noun from trade (v.).
tradesman (n.): 1590s, from genitive of trade (n.) + man (n.).
tradition (n.): late 14c., "statement, belief, or practice handed down from generation to generation," especially "belief or practice based on Mosaic law," from Old French tradicion "transmission, presentation, handing over" (late 13c.) and directly from Latin traditionem (nominative traditio) "delivery, surrender, a handing down, a giving up," noun of action from past participle stem of tradere "deliver, hand over," from trans- "over" (see trans-) + dare "to give" (see date (n.1)). The word is a doublet of treason (q.v.). Meaning "a long-established custom" is from 1590s. The notion is of customs, ways, beliefs, doctrines, etc. "handed down" from one generation to the next.
Nobody can make a tradition; it takes a century to make it. [Hawthorne, "Septimius Felton," 1872]
traditional (adj.): 1590s, "observing traditions;" c. 1600, "handed down as tradition," from tradition + -al (1). In reference to jazz, from 1950. Related: Traditionally; traditionalist.
traduce (v.): 1530s, "alter, change over, transport," from Latin traducere "change over, convert," also "lead in parade, make a show of, dishonor, disgrace," originally "lead along or across, bring through, transfer" (source also of French traduire, Spanish traducir, Italian tradurre), from trans- "across" (see trans-) + ducere "to lead" (see duke (n.)). Sense of "defame, slander" in English is from 1580s, from Latin traducere in the sense of "scorn or disgrace," a figurative use from the notion of "to lead along as a spectacle." Related: Traduced; traducing.
traducer (n.): 1610s, agent noun from traduce (v.).
Trafalgar: cape in southwestern Spain, from Arabic taraf-al-garb "end of the west," or taraf-agarr "end of the column" (in reference to the pillars of Hercules). The British naval victory over the French there was fought Oct. 21, 1805; hence London's Trafalgar Square, named in commemoration of it.
traffic (n.): c. 1500, "trade, commerce," from Middle French trafique (15c.), from Italian traffico (14c.), from trafficare "carry on trade," of uncertain origin, perhaps from a Vulgar Latin *transfricare "to rub across," from Latin trans- "across" (see trans-) + fricare "to rub" (see friction), with the original sense of the Italian verb being "touch repeatedly, handle."

Or the second element may be an unexplained alteration of Latin facere "to make, do." Klein suggests ultimate derivation of the Italian word from Arabic tafriq "distribution." Meaning "people and vehicles coming and going" first recorded 1825. Traffic jam is 1917, ousting earlier traffic block (1895). Traffic circle is from 1938.
traffic (v.): 1540s, "to buy and sell," from traffic (n.) and preserving the original commercial sense. Related: Trafficked; trafficking; trafficker. The -k- is inserted to preserve the "k" sound of -c- before a suffix beginning in -i-, -y-, or -e- (compare picnic/picnicking, panic/panicky, shellacshellacked).
tragedian (n.): "writer of tragedies," late 14c., from Old French tragediane (Modern French tragédien), from tragedie (see tragedy). Another word for this was tragician (mid-15c.). Meaning "actor in tragedies" is from 1590s. French-based fem. form tragedienne is from 1851. In late classical Greek, tragodos was the actor, tragodopoios the writer.
tragedy (n.): late 14c., "play or other serious literary work with an unhappy ending," from Old French tragedie (14c.), from Latin tragedia "a tragedy," from Greek tragodia "a dramatic poem or play in formal language and having an unhappy resolution," apparently literally "goat song," from tragos "goat" + oide "song" (see ode).

The connection may be via satyric drama, from which tragedy later developed, in which actors or singers were dressed in goatskins to represent satyrs. But many other theories have been made (including "singer who competes for a goat as a prize"), and even the "goat" connection is at times questioned. Meaning "any unhappy event, disaster" is from c. 1500.
tragi-comedy (n.): also tragicomedy, "characterized by both serious and comic scenes," 1570s, from Middle French tragicomédie (1540s), from Italian tragicommedia, from Late Latin tragicomoedia, contraction of tragicocomoedia (Plautus), from tragicus (see tragic) + comoedia (see comedy).
tragi-comic (adj.): "both serious and tragic," 1680s; see tragi-comedy + -ic. Related: Tragi-comical (1560s).
tragic (adj.): 1540s, "calamitous, disastrous, fatal" ("resembling the actions in a stage tragedy"), shortened from tragical (late 15c.), modeled on Latin tragicus, from Greek tragikos "of or pertaining to tragedy; stately, majestic; plaintive," literally "goatish, of or pertaining to a goat," and perhaps referring to a satyr impersonated by a goat singer or satyric actor, from tragodia (see tragedy). Tragic flaw (1913) translates Greek hamartia. Related: Tragically.
tragus (n.): "eminence at the opening of the ear," 1690s, Modern Latin, from Greek tragos in this sense (Rufus of Ephesus), properly "he-goat;" so called for the tuft of hair which grows there, which resembles a goat's beard.