Online Etymology Dictionary

tete (n.): as a type of women's tall dressed hair or wig, 1756, from French tête "head" (see tete-a-tete).
tete-a-tete (n.): "a private meeting," French, tête-à-tête, literally "head-to-head," from Old French teste "head" (see tester (n.2)). The adjective, "privately," is recorded from 1728.
tether (n.): late 14c., "rope for fastening an animal," probably from Old Norse tjoðr "tether," from Proto-Germanic *teudran (cf. Danish tøir, Swedish tjuder, Old Frisian tiader, Middle Dutch tuder, Dutch tuier "line, rope," Old High German zeotar "pole of a cart"), from PIE root *deu- "to fasten" + instrumentive suffix *-tro-. Figurative sense of "measure of one's limitations" is attested from 1570s.
tether (v.): late 15c., from tether (n.). Related: Tethered; tethering.
tetherball (n.): also tether-ball, 1900, from tether (n.) + ball (n.1).
Tethys: geologists' name for the sea that anciently lay between Eurasia and Africa-Arabia, 1893, from the name of a Greek sea goddess, sister and consort of Oceanus.
Teton: member of a western Sioux people, 1806, from Dakota titonwan, literally "dwellers on the prairie," from thi + huwa. Not related to the Grand Teton mountain range.
tetra-: word-forming element meaning "four," from Greek tetra-, combining form of tettares, tessares "four" (see four).
tetracycline (n.): 1952, with chemical suffix -ine (2) + tetracyclic "containing four fused hydrocarbon rings," from tetra- + cyclic (see cycle (n.)).
tetrad (n.): 1650s, from Greek tetras (comb. form tetrad-) "group of four" (see tetra-).
tetragrammaton (n.): c.1400, from Greek (to) tetragrammaton "(the word) of four letters," from tetra- "four" (see four) + gramma (genitive grammatos) "letter, something written" (see grammar). The Hebrew divine name, transliterated as YHWH, usually vocalized in English as "Jehovah" or "Yahweh."
tetrahedron (n.): solid figure contained by four triangular surfaces, 1560s, from Late Greek tetraedron, originally neuter of tetraedros (adj.) "four-sided," from tetra- "four" + hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- "to sit" (see sedentary).
tetralogy (n.): 1650s, from Greek tetralogia, from tetra- (see tetra-) + -logia (see -logy).
tetrameter (n.): 1610s, from Latin tetrametrus, from Greek tetrametron "verse of four measures," originally neuter of tetrametros (adj.) "having four measures," from tetra- "four" (see tetra-) + metron "measure" (see meter (n.2)).
tetrapod (n.): 1826, from Modern Latin tetrapodus, from Greek tetrapous, from tetra- (see tetra-) + pous (see foot n.)).
tetrarch (n.): late Old English tetrarche "ruler of one of four divisions of a kingdom or province," from Late Latin tetrarcha, from Greek tetrarkhes "leader of four companies, tetrarch," from tetra- "four" (see tetra-) + arkhein "to rule" (see archon). Applied generally to subordinate rulers in the Roman Empire, especially in Syria.
Teutonic (adj.): c.1600, "of or pertaining to the Germanic languages and to peoples or tribes who speak or spoke them," from Latin Teutonicus, from Teutones, name of a tribe that inhabited coastal Germany and devastated Gaul 113-101 B.C.E., probably from a Proto-Germanic word related to Old High German diot "people" (see Dutch), from *teuta, the common PIE word for "people" (cf. Lithuanian tauto, Oscan touto, Old Irish tuath, Gothic þiuda, Old English þeod).

Used in English in anthropology to avoid the modern political association of German; but in this anthropoligical sense French uses germanique and German uses germanisch, because neither uses its form of German for the narrower national meaning (cf. French allemand, see Alemanni; and German deutsch). In Finnish, Germany is Saksa "Land of the Saxons."

The Teutonic Knights (founded c.1191) were a military order of German knights formed for service in the Holy Land, but who later crusaded in then-pagan Prussia and Lithuania. The Teutonic cross (1882) was the badge of the order. Teuton "a German" is attested from 1833.
Tex: nickname for a Texan, by 1903, from Texas.
Tex-Mex (adj.): by 1914, from Texas + Mexico.
Texas: Mexican province, briefly an independent nation and now a U.S. state, from Spanish Texas, Tejas, earlier pronounced "ta-shas," originally an ethnic name, from Caddo (eastern Texas Indian tribe) taysha "friends, allies," written by the Spanish as a plural. An earlier noun for "Texan of Mexican background" was Texican (1863). Baseball Texas-leaguer is recorded from 1905.
text (n.): late 14c., "wording of anything written," from Old French texte, Old North French tixte (12c.), from Medieval Latin textus "the Scriptures, text, treatise," in Late Latin "written account, content, characters used in a document," from Latin textus "style or texture of a work," literally "thing woven," from past participle stem of texere "to weave," from PIE root *tek- "to weave, to fabricate, to make; make wicker or wattle framework" (see texture).
An ancient metaphor: thought is a thread, and the raconteur is a spinner of yarns -- but the true storyteller, the poet, is a weaver. The scribes made this old and audible abstraction into a new and visible fact. After long practice, their work took on such an even, flexible texture that they called the written page a textus, which means cloth. [Robert Bringhurst, "The Elements of Typographic Style"]
text (v.): "to send a text message by mobile system," 2005; see text (n.). Related: Texted; texting. It formerly was a verb meaning "to write in text letters" (1590s).
textbook (n.): also text-book, 1779, from text (n.) + book (n.).
textile (n.): 1620s, from Latin textilis "woven, fabric, cloth," noun use of textilis "woven," from texere "to weave," from PIE root *tek- "to make" (see texture).
textual (adj.): late 14c., from Latin textus (see text) + -al (1). Related: Textually.
texture (n.): early 15c., "network, structure," from Middle French texture, from Latin textura "web, texture, structure," from stem of texere "to weave," from PIE root *tek- "to weave, to fabricate, to make; make wicker or wattle framework" (cf. Sanskrit taksati "he fashions, constructs," taksan "carpenter;" Avestan taša "ax, hatchet," thwaxš- "be busy;" Old Persian taxš- "be active;" Greek tekton "carpenter," tekhne "art;" Old Church Slavonic tesla "ax, hatchet;" Lithuanian tasau "to carve;" Old Irish tal "cooper's ax;" Old High German dahs, German Dachs "badger," literally "builder;" Hittite taksh- "to join, unite, build"). Meaning "structural character" is recorded from 1650s.
TGIF: also T.G.I.F., by 1946, slang abbreviation of "Thank God (or "goodness"), it's Friday" (end of the work week).
th: A sound found chiefly in words of Old English, Old Norse or Greek origin, unpronounceable by Normans and many other Europeans. In Greek, the sound corresponds etymologically to Sanskrit -dh- and English -d-; and it was represented graphically by -TH- and at first pronounced as a true aspirate (as still in English outhouse, shithead, etc.). But by 2c. B.C.E. the Greek letter theta was in universal use and had the modern "-th-" sound. Latin had neither the letter nor the sound, however, and the Romans represented Greek theta by -TH-, which they generally pronounced, at least in Late Latin, as simple "-t-" (passed down to Romanic languages, e.g. Spanish termal "thermal," teoria "theory," teatro "theater").

In Germanic languages it represents PIE -t- and was common at the start of words or after stressed vowels. To represent it, Old English and Old Norse used the characters ð "eth" (a modified form of -d-) and þ "thorn," which originally was a rune. Old English, unlike Old Norse, seems never to have standardized which of the two versions of the sound ("hard" and "soft") was represented by which of the two letters.

The digraph -th- sometimes appears in early Old English, on the Roman model, and it returned in Middle English with the French scribes, driving out eth by c.1250, but thorn persisted, especially in demonstratives (þat, þe, þis, etc.), even as other words were being spelled with -th-. The advent of printing dealt its death-blow, however, as types were imported from continental founders, who had no thorn. For a time y was used in its place (especially in Scotland), because it had a similar shape, hence ye for the in historical tourist trap olde shoppes (it never was pronounced "ye," only spelled that way).

The awareness that some Latin words in t- were from Greek th- encouraged over-correction in English and created unetymological forms such as Thames and author, while some words borrowed from Romanic languages preserve, on the Roman model, the Greek -th- spelling but the simple Latin "t" pronunciation (e.g. Thomas and thyme).
Thaddeus: masc. proper name, from Latin Thaddaeus, from Greek Thaddaios, from Talmudic Hebrew Tadday.
Thai: 1808, native name, from Tai, literally "free." Thai stick "Asian marijuana cigarette" is attested by 1976.
Thailand: from Thai, indigenous name of the inhabitants, + land (n.). Cf. Siam.
thalamus (n.): 1753, "the receptacle of a flower," Modern Latin, from Latin thalamus "inner chamber," from Greek thalamos "inner chamber, bedroom," related to thalame "den, lair," tholos "vault, vaulted building." Used since 1756 of a part of the forebrain where a nerve appears to originate.
thalassemia (n.): from thalasso-, comb. form of Greek thalassa "sea" + haima "blood" (see -emia).
Thalia: fem. proper name, from Greek Thaleia, literally "luxuriant, blooming," from thallein "to bloom" (see thallus). Eighth of the Muses, presiding over comedy and idyllic poetry. Also one of the three Graces, patroness of festive meetings.
Thalidomide (n.): 1958, from "phthalimidoglutarimide," based on abbreviated form of naphthalene; a morning-sickness drug responsible for severe birth defects in Europe from 1956 to 1961, when it was withdrawn. It was never approved for use in America thanks to the efforts of Dr. Helen Brooke Taussig. Thalidomide baby is attested from 1962.
thallium (n.): rare metallic element, 1861, Modern Latin, from Greek thallos "young shoot, green branch" (see thallus) + element name ending -ium. So called by its discoverer, Sir William Crookes (1832-1919), from the green line in its spectrum by which he detected it.
thallus (n.): Latin, from Greek thallos "green shoot, twig," related to thalia "abundance," thalos "scion, child," ultimately from PIE root *dhal- "to bloom" (cf. Old Irish duilesc, a type of algae).
thalweg (n.): 1831, from German Thalweg "path along the bottom of a valley," from thal (see dale) + weg (see way).
Thames: Old English Temese, from Latin Tamesis (51 B.C.E.), from Brit. Tamesa, an ancient Celtic river name perhaps meaning "the dark one." The -h- is unhistorical (see th).
Thammuz: 1530s, from Hebrew tammuz, tenth month of the Jewish civil year, fourth of the sacred, covering parts of June and July; also the name of a Syrian deity equivalent to Phoenician Adon, whose festival began with the new moon of this month (cf. Tammuz).
than (conj.): Old English þan, conjunctive particle used after a comparative adjective or adverb, from þanne, þænne, þonne "then" (see then). Developed from the adverb then, and not distinguished from it in spelling until c.1700.

The earliest use is in West Germanic comparative forms, i.e. bigger than (cf. Dutch dan, German denn), which suggests a semantic development from the demonstrative sense of then: A is bigger than B, evolving from A is bigger, then ("after that") B. Or the word may trace to Old English þonne "when, when as," such as "When as" B is big, A is more (so).
thanage (n.): c.1400, from Anglo-French thaynage (c.1300), from English thane + Old French suffix -age (see -age).
thanatology (n.): "scientific study of death," 1842, from Greek thanatos "death" (from PIE *dhwene- "to disappear, die," perhaps from root meaning "dark, cloudy") + -logy.

Thanatism (1900) is the belief that at death the soul ceases to exist. Hence also thanatos. In 1970s, some undertakers made a bid to be called thanatologists; from 1974 that word was used in reference to specialists in the needs of the terminally ill.
thanatos (n.): "death instinct," 1935, in Freudian psychology, from Greek thanatos (see thanatology).
thane (n.): Old English þegn "military follower," also "servant, attendant," from Proto-Germanic *thegnas (cf. Old Saxon thegan "follower, warrior, boy," Old Norse þegn "thane, freeman," Old High German thegan, German Degen "thane, warrior, hero"), from PIE *tek-no- (cf. Sanskrit takman "descendant, child," Greek teknon "child"), from root *tek- "to beget, give birth to" (cf. Greek tekos "child, the young of animals," tokos "childbirth, offspring, produce of money, interest"). Also used in Old English for "disciple of Christ." Specific sense of "man who ranks between an earl and a freeman" is late 15c.

The modern spelling is from Scottish, where early 13c. it came to mean "chief of a clan, king's baron," and probably predominated in English due to influence of "Macbeth;" normal orthographic changes from Old English ðegn would have produced Modern English *thain. Some historians now use thegn to distinguish Anglo-Saxon thanes from Scottish thanes.
thank (v.): Old English þancian "to give thanks," from Proto-Germanic *thankojan (cf. Old Saxon thancon, Old Norse þakka, Danish takke, Old Frisian thankia, Middle Dutch, German danken "to thank"), from *thankoz "thought, gratitude," from PIE root *tong- "to think, feel." For sense evolution, cf. related Old English noun þanc, þonc, originally "thought," but by c.1000 "good thoughts, gratitude." The whole group is from the same root as think (q.v.). In ironical use, "to blame," from 1550s. To thank (someone) for nothing is recorded from 1703. Related: Thanked; thanking.
thank you: phrase attested by c.1400, short for I thank you; as a noun, from 1792.
thankful (adj.): Old English þancfulle; see thank + -ful. Related: Thankfully; thankfulness.
thankless (adj.): "likely to not be rewarded with thanks," 1540s, from thank + -less. Related: Thanklessly.
thanks (n.): mid-14c., from thank (v.).