thew (n.) Look up thew at Dictionary.com
Old English þeaw; see thews.
thews (n.) Look up thews at Dictionary.com
Old English þeawes "customs, manners, personal qualities," plural of þeaw "habit, custom," from Proto-Germanic *thawaz (cf. Old Saxon thau "usage, custom, habit," Old High German thau "discipline"); no certain cognates outside West Germanic and of unknown origin. Meaning "bodily powers or parts indicating strength, good physique" is attested from 1560s, from notion of "good qualities." Acquired a sense of "muscular development" when it was revived by Scott (1818).
they (pron.) Look up they at Dictionary.com
c.1200, from Old Norse þeir, originally masculine plural demonstrative pronoun, from Proto-Germanic *thai, nominative plural pronoun, from PIE *to- (see that). Gradually replaced Old English hi, hie, plurals of he, heo, hit (see he, she, it) by c.1400. Colloquial use for "anonymous people in authority" is attested from 1886.
thiamin (n.) Look up thiamin at Dictionary.com
also thiamine, alternative name for vitamin B1, 1937, coined by Dr. R.R. Williams from thio-, indicating the presence of sulfur, comb. form of Greek theion "sulfur," + amine, indicating the amino group. Or the second element might be from vitamin.
thick (adj.) Look up thick at Dictionary.com
Old English þicce "not thin, dense," from Proto-Germanic *theku-, *thekwia- (cf. Old Saxon thikki, Old High German dicchi, German dick, Old Norse þykkr, Old Frisian thikke), from PIE *tegu- "thick" (cf. Gaelic tiugh).

Secondary Old English sense of "close together" is preserved in thickset and proverbial phrase thick as thieves (1833). Meaning "stupid" is first recorded 1590s. Phrase thick and thin is in Chaucer (late 14c.); thick-skinned is attested from 1540s; in figurative sense from c.1600. To be in the thick of some action, etc., "to be at the most intense moment" is from 1680s, from a Middle English noun sense.
thicken (v.) Look up thicken at Dictionary.com
early 15c. (transitive), 1590s (intransitive), from thick + -en (1). Related: Thickened; thickening. An earlier verb was Old English þiccian.
thickening (n.) Look up thickening at Dictionary.com
"substance used to thicken something," 1839, verbal noun from thicken.
thicket (n.) Look up thicket at Dictionary.com
late Old English þiccet, from þicce (see thick) + denominative suffix -et.
thickness (n.) Look up thickness at Dictionary.com
Old English þicness; see thick + -ness.
thickset (adj.) Look up thickset at Dictionary.com
mid-14c., thikke sette "with parts or things set close together" (of grass on a sward, etc.), from thick + set (v.). Meaning "stocky, strong and square-built" is recorded from 1724.
thief (n.) Look up thief at Dictionary.com
Old English þeof, from Proto-Germanic *theubaz (cf. Old Frisian thiaf, Old Saxon thiof, Middle Dutch dief, Old High German diob, German dieb, Old Norse þiofr, Gothic þiufs), probably from PIE *teup- (cf. Lithuanian tupeti "to crouch down").
thieve (v.) Look up thieve at Dictionary.com
Old English þeofian, from þeof (see thief). Rare in Old English, not common until 17c. Thieving first attested 1520s.
thievery (n.) Look up thievery at Dictionary.com
1560s, from thieve + -ery.
thievish (adj.) Look up thievish at Dictionary.com
mid-15c., "of or pertaining to thieves," from thieve + -ish. Meaning "inclined to steal" is from 1530s. Related: Thievishly; thievishness.
thigh (n.) Look up thigh at Dictionary.com
Old English þeoh, þeh, from Proto-Germanic *theukhom (cf. Old Frisian thiach, Old Dutch thio, Dutch dij, Old Norse þjo, Old High German dioh), from PIE *teuk- from root *teu- "to swell" (cf. Lithuanian taukas, Old Church Slavonic tuku, Russian tuku "fat of animals;" Lithuanian tukti "to become fat;" Greek tylos "callus, lump," tymbos "burial mound, grave, tomb;" Old Irish ton "rump;" Latin tumere "to swell," tumulus "raised heap of earth," tumor "a swelling;" Middle Irish tomm "a small hill," Welsh tom "mound"). Thus thigh is literally "the thick or fat part of the leg."
thigmotropism (n.) Look up thigmotropism at Dictionary.com
1900, from thigmo-, comb. form meaning "touch," from Greek thigma "touch" + tropism.
thilk Look up thilk at Dictionary.com
"the very thing," early 13c., from þe "the" (see the) + ilce "same" (see ilk).
thimble (n.) Look up thimble at Dictionary.com
Old English þymel "sheath or covering for the thumb," from thuma (see thumb) + -el, suffix used in forming names of instruments (cf. handle). Excrescent -b- began mid-15c. (cf. humble, nimble). Originally of leather, metal ones came into use 17c. Thimblerig, con game played with three thimbles and a pea or button, is attested from 1825 by this name, though references to thimble cheats, probably the same swindle, date back to 1716.
thin (adj.) Look up thin at Dictionary.com
Old English þynne "narrow, lean, scanty," from Proto-Germanic *thunnuz, *thunw- (cf. West Frisian ten, Middle Low German dunne, Dutch dun, Old High German dunni, German dünn, Old Norse þunnr), from PIE *tnus-, *tnwi-, from weak grade of root *ten- "stretch" (cf. Latin tenuis "thin, slender;" see tenet).
These our actors ... were all Spirits, and Are melted into Ayre, into thin Ayre. [Shakespeare, "The Tempest," IV.i.150, 1610]
Thin-skinned is attested from 1590s; the figurative sense of "touchy" is from 1670s.
thin (v.) Look up thin at Dictionary.com
Old English þynnian "to make thin" (cf. German dünnen, Dutch dunnen), from thin (adj.). Intransitive sense of "to become less numerous" is attested from 1743; that of "to become thinner" is recorded from 1804. Related: Thinned; thinning.
thine (pron.) Look up thine at Dictionary.com
Old English þin, possessive pronoun (originally genitive of þu "thou"), from Proto-Germanic *thinaz (cf. Old Frisian, Old Saxon thin, Middle Dutch dijn, Old High German din, German dein, Old Norse þin), from PIE *t(w)eino-, suffixed form of second person singulsr pronomial base *tu-. A brief history of the second person pronoun in English can be found here; see also thou.
thing (n.) Look up thing at Dictionary.com
Old English þing "meeting, assembly," later "entity, being, matter" (subject of deliberation in an assembly), also "act, deed, event, material object, body, being," from Proto-Germanic *thengan "appointed time" (cf. Old Frisian thing "assembly, council, suit, matter, thing," Middle Dutch dinc "court-day, suit, plea, concern, affair, thing," Dutch ding "thing," Old High German ding "public assembly for judgment and business, lawsuit," German ding "affair, matter, thing," Old Norse þing "public assembly"). Some suggest an ultimate connection to PIE root *ten- "stretch," perhaps on notion of "stretch of time for a meeting or assembly."

For sense evolution, cf. French chose, Spanish cosa "thing," from Latin causa "judicial process, lawsuit, case;" Latin res "affair, thing," also "case at law, cause." Old sense is preserved in second element of hustings and in Icelandic Althing, the nation's general assembly.

Used colloquially since c.1600 to indicate things the speaker can't name at the moment, often with various meaningless suffixes, e.g. thingumbob (1751), thingamajig (1824). Southern U.S. pronunciation thang attested from 1937. The thing "what's stylish or fashionable" is recorded from 1762. Phrase do your thing "follow your particular predilection," though associated with hippie-speak of 1960s is attested from 1841.
thingamajig (n.) Look up thingamajig at Dictionary.com
also thingumajig, 1824, see thing.
think (v.) Look up think at Dictionary.com
Old English þencan "conceive in the mind, think, consider, intend" (past tense þohte, p.p. geþoht), probably originally "cause to appear to oneself," from Proto-Germanic *thankjan (cf. Old Frisian thinka, Old Saxon thenkian, Old High German denchen, German denken, Old Norse þekkja, Gothic þagkjan); Old English þencan is the causative form of the distinct Old English verb þyncan "to seem or appear" (past tense þuhte, past participle geþuht), from Proto-Germanic *thunkjan (cf. German dünken, däuchte). Both are from PIE *tong- "to think, feel" which also is the root of thought and thank. The two meanings converged in Middle English and þyncan "to seem" was absorbed, except for archaic methinks "it seems to me." Jocular past participle thunk (not historical, but by analogy of drink, sink, etc.) is recorded from 1876.
think tank (n.) Look up think tank at Dictionary.com
also think-tank, 1959 as "research institute" (first reference is to Center for Behavioral Sciences, Palo Alto, Calif.); it had been colloquial for "the brain" since 1905. See think + tank (n.).
thinner (n.) Look up thinner at Dictionary.com
liquid used to dilute paint, ink, etc., 1904, agent noun from thin (v.).
third (adj.) Look up third at Dictionary.com
Old English metathesis of þridda, from Proto-Germanic *thridjas (cf. Old Frisian thredda, Old Saxon thriddio, Middle Low German drudde, Dutch derde, Old High German dritto, German dritte, Old Norse þriðe, Gothic þridja), from PIE *tritjos (cf. Sanskrit trtiyas, Avestan thritya, Greek tritos, Latin tertius, Old Church Slavonic tretiji, Lithuanian trecias, Old Irish triss).

Related to Old English þreo (see three). Metathesis of thrid into third is attested from c.950 in Northumbria, but thrid was prevalent up to 16c. The noun meaning "third part of anything" is recorded from late 14c. Third rail in electric railway sense is recorded from 1890. Third World War as a possibility first recorded 1947. Third-rate "of poor quality" is from 1814, ultimately from classification of ships (1640s); third class in railway travel is from 1839. Third Reich (1930) is a partial translation of German drittes Reich (1923). Third party in law, insurance, etc., is from 1818.
third degree (n.) Look up third degree at Dictionary.com
"intense interrogation by police," 1900, probably a reference to Third Degree of master mason in Freemasonry (1772), the conferring of which included an interrogation ceremony. Third degree as a measure of severity of burns (most severe) is attested from 1866, from French (1832); in American English, as a definition of the seriousness of a particular type of crime (the least serious type) it is recorded from 1865.
Third World (n.) Look up Third World at Dictionary.com
1963, from French tiers monde, formulated 1952 by French economic historian Alfred Sauvy (1898-1990) on model of the third estate (French tiers état) of Revolutionary France; his first world (The West) and second world (the Soviet bloc) never caught on.
thirst (v.) Look up thirst at Dictionary.com
Old English þyrstan (see thirst (n.)); the figurative sense of the verb was present in Old English. Related: Thirsted; thirsting.
thirst (n.) Look up thirst at Dictionary.com
Old English þurst, from West Germanic *thurstus (cf. Old Saxon thurst, Frisian torst, Dutch dorst, Old High German and German durst), from Proto-Germanic *thurs-, from PIE root *ters- "dry" (see terrain). Figurative sense of "vehement desire" is attested from c.1200.
thirsty (adj.) Look up thirsty at Dictionary.com
Old English þurstig; see thirst (n.) + -y (2).
thirteen (n.) Look up thirteen at Dictionary.com
early 15c., metathesis of Old English þreotene (Mercian), þreotiene (West Saxon), from þreo "three" (see three) + -tene (see -teen). Cf. Old Frisian thretten, Dutch dertien, German dreizehn.

Not an unlucky number in medieval England, but associated rather with the customary "extra item" (e.g. baker's dozen). Superstitions began with association with the Last Supper, and the unluckiness of 13 sitting down together to dine (attested from 1690s). Most of the modern superstitions (buildings with floor "12-A," etc.) have developed since 1890.
thirties (n.) Look up thirties at Dictionary.com
1827 as the years of someone's life between 30 and 39; 1830 as a decade of years in a given century. See thirty.
thirtieth Look up thirtieth at Dictionary.com
Middle English threttyth, from Old English þritigoða; see thirty + -th. Respelled 16c. to conform to new spelling of thirty.
thirty Look up thirty at Dictionary.com
early 15c. metathesis of Old English þritig, from þri, þreo "three" + -tig "group of ten" (see -ty (1)). Cf. Old Frisian thritich, Old Saxon thritig, Dutch dertig, Old High German drizzug, German dreissig. Thirty Years' War (1842) was a religious power struggle waged 1618-48, mainly on German soil. The symbol -30- as printer and telegrapher's code to indicate the last sheet or line of copy or a dispatch is recorded from 1895. In 20c. jargon of journalism, it came to be a traditional sign-off signal and slang word for "the end."
this Look up this at Dictionary.com
Old English þis, neuter demonstrative pronoun and adjective (masc. þes, fem. þeos), probably from a North Sea Germanic pronoun formed by combining the base *þa- (see that) with -s, which is probably identical with Old English se "the" (representing here "a specific thing"), but it may be Old English seo, imperative of see (v.) "to behold." Cf. Old Saxon these, Old Norse þessi, Dutch deze, Old Frisian this, Old High German deser, German dieser.

Once fully inflected, with 10 distinct forms (see table below); the oblique cases and other genders gradually fell away by 15c. The Old English plural was þæs (nominative and accusative), which in Northern Middle English became thas, and in Midlands and Southern England became thos. The Southern form began to be used late 13c. as the plural of that (replacing Middle English tho, from Old English þa) and acquired an -e (apparently from the influence of Middle English adjective plurals in -e; cf. alle from all, summe from sum "some"), emerging early 14c. as modern those.

About 1175 thes (probably a variant of Old English þæs) began to be used as the plural of this, and by 1200 it had taken the form these, the final -e acquired via the same mechanism that gave one to those.

Masc.Fem.Neut.Plural
Nom.þesþeosþisþas
Acc.þisneþasþisþas
Gen.þissesþisseþissesþissa
Dat.þissumþisseþissumþissum
Inst.þysþisseþysþissum
thistle (n.) Look up thistle at Dictionary.com
prickly herbaceous plant, Old English þistel, from Proto-Germanic *thikhstula (cf. Old High German distil, German Distel, Old Norse þistell, Danish tidsel), of unknown origin. Emblem of Scotland since 15c.
thither (adv.) Look up thither at Dictionary.com
Old English þider "to or toward that place," altered (by influence of its opposite hider) from earlier þæder "to that place," from Proto-Germanic *thadra- (cf. Old Norse þaðra "there"), from *tha (see that) + PIE suffix denoting motion toward (cf. Gothic -dre, Sanskrit -tra). The medial -th- developed in Middle English but was rare before early 16c. (cf. gather, murder, burden).
thixotropic (adj.) Look up thixotropic at Dictionary.com
1927, from thixotropy, coined in German from Greek thixis "touching" + trope "turning" (see trope (n.)).
tho Look up tho at Dictionary.com
contraction of though.
thole (v.) Look up thole at Dictionary.com
"to be subjected to or exposed to, to endure without complaint," now Scottish and Northern English dialect, from Old English þolian, from Proto-Germanic stem *thul- (cf. Old Saxon tholon, Old High German dolon, German geduld, Old Norse þola, Gothic þulan), cognate with Latin tolerare (see toleration).
thole (n.) Look up thole at Dictionary.com
"peg," from Old English þoll, from Proto-Germanic *thulnaz (cf. Old Norse þollr, Middle Low German dolle, East Frisian dolle, Dutch dol), of unknown origin. No record of the word in English from c.1000 to mid-15c.
Thomas Look up Thomas at Dictionary.com
from Greek Thomas, of Aramaic origin and said to mean "a twin" (John's gospel refers to Thomas as ho legomenos didymos "called the twin;" cf. Syriac toma "twin," Arabic tau'am "twin"). Before the Conquest, found only as the name of a priest. After 1066, one of the most common given names in English. Doubting Thomas is from John xx:25; A Thomist (1530s, from Medieval Latin Thomista, mid-14c.) is a follower of 13c. scholastic theologian St. Thomas Aquinas. (Also see Tom, Tommy).
Thompson Look up Thompson at Dictionary.com
type of sub-machine gun, 1919, named for U.S. Gen. John T. Thompson (1860-1940), who conceived it and whose company financed it.
thong (n.) Look up thong at Dictionary.com
Old English þwong "thong, narrow strip of leather (used as a cord, band, strip, etc.)," from Proto-Germanic *thwangaz (cf. Old Norse þvengr), from PIE root *twengh- "to press in on, to restrain." As a kind of sandal, first attested 1965; as a kind of bikini briefs, 1990.
Thor Look up Thor at Dictionary.com
Odin's eldest son, strongest of the gods though not the wisest, c.1020, from Old Norse Þorr, literally "thunder," from *þunroz, related to Old English þunor (see thunder).
thoracic (adj.) Look up thoracic at Dictionary.com
1650s, from Medieval Latin thoracicus, from Greek thorakikos, from thorax (see thorax).
thoracotomy (n.) Look up thoracotomy at Dictionary.com
1890, from thorax + -ectomy.
thoral (adj.) Look up thoral at Dictionary.com
1690s, from Latin torus "couch, marriage bed, stuffed cushion" + -al (1).