Online Etymology Dictionary

tamper (v.): 1560s, figurative use of tamper "to work in clay, etc., so as to mix it thoroughly," probably originally a variant of temper (v.), which is how it was initially spelled. Perhaps it is a dialectal workmen's pronunciation. Related: Tampered; tampering.
tamperproof (adj.): also tamper-proof, 1886, from tamper (v.) + proof.
tampion (n.): early 15c., "plug, bung," from Middle French tampon, nasalized variant of Old French tapon "piece of cloth to stop a hole" (late 14c.), a suffixed form of Frankish *tappo "stopper, plug," related to Old High German zapfo and Old English tæppa "stopper" (see tap (2)). Meaning "wooden plug for the muzzle of a gun" (to keep out rain or seawater) is recorded from 1620s.
tampon (n.): 1848, from French tampon, from Middle French tampon "plug" (see tampion). Tampax, proprietary name registered in U.S. 1932, is based on tampon.
tan (v.): late Old English tannian "to convert hide into leather" (by steeping it in tannin), from Medieval Latin tannare "tan, dye, a tawny color" (c.900), from tannum "crushed oak bark," used in tanning leather, probably from a Celtic source (e.g. Breton tann "oak tree"). The meaning "make brown by exposure to the sun" first recorded 1520s. To tan (someone's) hide in the figurative sense is from 1660s. Related: Tanned; tanning.
tan (n.): "bronze color imparted to skin by exposure to sun," 1749, see tan (v.). As a simple name for a brownish color, in any context, it is recorded from 1888. The adjective tan "of the color of tanned leather" is recorded from 1660s.
tanager (n.): small American oscine bird, 1844, from Modern Latin tanagra, named 1758 by Linnaeus, alteration of Portuguese tangara, from Tupi (Brazil) tangara.
tandem: 1785, "carriage pulled by horses harnessed one behind the other," punning use of Latin tandem "at length (of time)," from tam "so" + demonstrative suffix -dem. Transferred by 1884 to bicycles with two seats.
tandoor (n.): 1660s, from Turkish pronunciation of Persian and Arabic tannur "oven, portable furnace" (see tandoori).
tandoori (n.): type of Indian cooking, 1958, from adjectival form of Urdu or Punjabi tandur "cooking stove," from Turkish tandur, from Turkish pronunciation of Arabic and Persian tannur "oven, portable furnace," of Semitic origin.
tang (n.): mid-14c., "serpent's tongue" (thought to be a stinging organ), later "sharp extension of a metal blade" (1680s), from Old Norse tangi "spit of land, pointed metal tool," perhaps related to tunga "tongue" (see tongue). Figurative sense of "a sharp taste" is first recorded mid-15c.; that of "suggestion, trace" is from 1590s. The fish (1734) so called for their spines.
tangelo (n.): "hybrid of a tangerine and a pomelo," 1904, the word formed like the fruit.
tangent (adj.): 1590s, "meeting at a point without intersecting," from Latin tangentem (nominative tangens), present participle of tangere "to touch," from PIE root *tag- "to touch, to handle" (cf. Latin tactus "touch," Greek tetagon "having seized," Old English þaccian "stroke, strike gently"). First used by Danish mathematician Thomas Fincke in "Geomietria Rotundi" (1583). Extended sense of "slightly connected with a subject" is first recorded 1825. The noun also is attested from 1590s.
tangental (adj.): 1849, from tangent + -al (1). Related: Tangentally.
tangential (adj.): 1620s, see tangent; figurative sense of "divergent, erratic" is from 1787. Related: Tangentially.
tangerine (n.): 1842, from tangerine orange (1841) "an orange from Tangier," seaport in northern Morocco, from which it was originally imported to Britain. The place name is from Latin Tinge. As a color name, attested from 1899.
tangible (adj.): 1580s, "capable of being touched," from Middle French tangible, from Late Latin tangibilis "that may be touched," from Latin tangere "to touch" (see tangent). Sense of "material" (e.g. tangible reward) is first recorded 1610s; that of "able to be realized or dealt with" is from 1709.
tangle (n.): 1610s, "a tangled condition," from tangle (v.).
tangle (v.): mid-14c., nasalized variant of tagilen "to involve in a difficult situation, entangle," from a Scandinavian source (cf. dialectal Swedish taggla "to disorder," Old Norse þongull "seaweed"). In reference to material things, from c.1500. Meaning "to fight with" is American English, first recorded 1928. Related: Tangled; tangling. Tanglefoot (1859) was Western American English slang for "strong whiskey."
tango (n.): syncopated ballroom dance, 1913, from Argentine Spanish tango, originally the name of an African-American drum dance, probably from a Niger-Congo language (cf. Ibibio tamgu "to dance"). Phrase it takes two to tango was a song title from 1952.
tangram (n.): "Chinese geometric puzzle," 1864, said to be an arbitrary formation based on anagram, etc. First element perhaps Chin. t'an "to extend," or t'ang, commonly used in Cantonese for "Chinese." Some suggest it is the name of the inventor, "but no such person is known to Chinese scholars" [OED]. Another theory involves the Tanka people, who were involved in the opium trade, and Western sailors who discovered the puzzle from their Tanka girlfriends. Perhaps from an obscure sense of tram. The Chinese name is Ch'i ch'iao t'u "seven ingenious plan."
tangy (adj.): 1875, from tang + -y (2). Figurative use by 1948. Related: Tanginess.
tanist (n.): "elected heir of a Celtic chief," 1530s, from Gaelic tanaiste, literally "parallel, second," from Old Irish tanaise "designated successor," from Celtic *tani-hessio- "one who is waited for."
tank (n.): 1610s, "pool or lake for irrigation or drinking water," a word originally brought by the Portuguese from India, ultimately from Gujarati tankh "cistern, underground reservoir for water," Marathi tanken, or tanka "reservoir of water, tank."

Perhaps from Sanskrit tadaga-m "pond, lake pool," and reinforced in later sense of "large artificial container for liquid" (1680s) by Portuguese tanque "reservoir," from estancar "hold back a current of water," from Vulgar Latin *stanticare (see stanch). But others say the Portuguese word is the source of the Indian ones.

Meaning "fuel container" is recorded from 1902. Military use originated 1915, partly as a code word, partly because they looked like benzene tanks. They were first used in action at Pozieres ridge, on the Western Front, Sept. 15, 1916. Slang meaning "detention cell" is from 1912.
tank (v.): "to lose or fail," 1976, originally in tennis jargon, but said there to be from boxing, from tank (n.) in some sense. Related: Tanked; tanking. Adjective tanked "drunk" is from 1893.
tank top (n.): 1968, from tank suit "one-piece bathing costume" (1920s), so called because it was worn in a swimming tank (n.), i.e. pool.
tanka: form of Japanese verse, from Japanese tanka, from tan "short" + ka "song."
tankard (n.): c.1300, "large tub-like vessel," corresponding to Middle Dutch tanckaert, meaning the same thing, but both of unknown origin. A guess hazarded in OED is that it is a transposition of *kantard, from Latin cantharus. Meaning "drinking vessel" is first recorded late 15c.
tanker (n.): "ship for carrying oil or other liquid cargo," 1900, from tank (n.).
tanner (n.): "sixpence," slang word first recorded 1811, of unknown origin. J.C. Hotten, lexicographer of Victorian slang, thinks it may be from tanner and skin, rhyming slang for "thin," presumably in reference to the smallness of the coin. Not to be confused with tenner, slang for "ten pound note," which dates from 1861.
tannery (n.): c.1400, "process of tanning;" see tan (v.) + -ery. Meaning "place where tanning is done" is from 1736.
tannin (n.): vegetable substance capable of converting animal hide to leather, 1802, from French tannin (1798), from tan "crushed oak bark containing tannin" (see tan (v.)). Tannic acid first recorded 1836, from French acide tannique, inroduced 1834 by Pelouze.
tansy (n.): (Tanacetum vulgare), mid-13c., from Old French tanesie (13c.), from Gallo-Romance *tanaceta, from Late Latin tanacetum "wormwood," from shortened form of Greek athanasia "immortality," so called probably for its persistence. English folklore associates it with pregnancy, either as an aid to contraception or to provoke miscarriage.
tantalize (v.): 1590s, from Latin Tantalus, from Greek Tantalos, king of Phrygia, son of Zeus, punished in the afterlife (for an offense variously given) by being made to stand in a river up to his chin, under branches laden with fruit, all of which withdrew from his reach whenever he tried to eat or drink. His story was known to Chaucer (c.1369).
tantalizing (adj.): mid-17c., present participle adjective from tantalize. Related: Tantalizingly.
Tantalus: Greek Tantalos, king of Phrygia, perhaps literally "the Bearer" or "the Sufferer," by dissimilation from *tal-talos, a reduplication of PIE root *tel-, *tol- "to bear, carry, support" (see extol). Cf. tantalize.
tantamount (adj.): 1640s, from verbal phrase tant amount "be equivalent" (1620s), from Anglo-French tant amunter "amount to as much" (late 13c.), from Old French tant "as much" (from Latin tantus, from tam "so") + amonter "amount to, go up" (see amount).
tantra: type of Hindu religious book, 1799, from Sanskrit tantram, literally "loom, warp," hence "groundwork, system, doctrine," from tan "to stretch, extend," from PIE root *ten- "to stretch, extend" (see tenet).
tantric (adj.): 1905, from tantra + -ic; used loosely in the West to denote erotic spiritualism.
tantrum (n.): 1714, originally colloquial, of unknown origin.
tanzanite (n.): violet-blue gemstone, 1968, named by Henry B. Platt, vice president of Tiffany & Co., because the stone was discovered in the African nation of Tanzania.
tao (n.): 1736, from Chinese tao "way, path, right way (of life), reason."
Taoism (n.): religious system founded by Lao Tzu (b. 604 B.C.E.), 1839, from Chinese tao "way, path, right way (of life), reason" + -ism.
tap (v.1): "strike lightly," c.1200, from Old French taper "tap, rap, strike," from a Gallo-Romance or Germanic source ultimately imitative of the sound of rapping. Meaning "to designate for some duty or for membership" is recorded from 1952, from notion of a tap on the shoulder. Related: Tapped; tapping.
tap (n.2): "light blow or stroke," late 14c., from tap (v.1). Tap dancer first recorded 1927, from tap (n.) in the sense of "metal plate over the heel of a shoe" (1680s).
tap (n.1): "stopper, faucet," Old English tæppa, from Proto-Germanic *tappon (cf. Middle Dutch tappe, Dutch tap, Old High German zapfo, German zapfen). Originally a tapering cylindrical peg (hence taproot). Phrase on tap "ready for use" is recorded from late 15c.
tap (v.2): "to supply with a tap," Old English tæppian, from source of tap (n.1). Meaning "to draw liquor with a tap" is from mid-15c. Extended sense of "make use of" is first recorded 1570s. Meaning "to listen in secretly" (1869), originally with reference to telegraph wires. Tapped out "broke" is 1940s slang, perhaps from the notion of having tapped all one's acquaintances for loans already (cf. British slang on the tap "begging, making requests for loans," 1932).
tap (n.3): "device to listen in secretly on telephone calls," 1923, from tap (v.2) in the "listen secretly" sense.
tape (n.): Old English tæppe "narrow strip of cloth used for tying, measuring, etc.," of uncertain origin, perhaps a back-formation from Latin tapete "carpet." The original short vowel became long in Middle English.

Tape recorder "device for recording sound on magnetic tape" first attested 1932; from earlier meaning "device for recording data on ticker tape" (1892), from tape in the sense of "paper strip of a printer" (1884). Tape-measure is attested from 1873; tape-delay is from 1968.
tape (v.): c.1600, from tape (n.); meaning "to make a tape recording" is from 1950. Related: Taped; taping.