Online Etymology Dictionary

terminal (n.): "end point of a railway line," 1888, from terminal (adj.); sense of "device for communicating with a computer" is first recorded 1954. Earlier "final part of a word" (1831).
terminate (v.): early 15c., "bring to an end," from Latin terminatus, past participle of terminare "to mark the end or boundary," from terminus "end, limit" (see terminus). Intransitive sense of "to come to an end" is recorded from 1640s; meaning "dismiss from a job" is recorded from 1973; that of "to assassinate" is from 1975. Related: Terminated; terminating.
termination (n.): late 14c., "authoritative resolution of a matter," from Old French terminacion (13c.) and directly from Latin terminationem (nominative terminatio) "a fixing of boundaries, a bounding, determining," noun of action from past participle stem of terminare "to mark the end or boundary," from terminus "end, limit" (see terminus). Meaning "end of a person's employment" is recorded from 1961; meaning "artificial end of a pregnancy" is attested from 1969; sense of "assasination" is recorded from 1975.
terminator (n.): 1770, "line of separation between the bright and dark parts of a moon or planet," from Late Latin terminator "he who sets bounds," agent noun from terminare "to mark the end or boundary," from terminus "end, limit" (see terminus). Meaning "one who terminates" (something) is attested from 1846.
terminer (n.): "a determining," legal term, from French terminer "to end," in Old French "to decide, rule on," from Latin terminare "to mark the end or boundary," from terminus "end, limit" (see terminus; also see oyer).
terminology (n.): 1770, from German Terminologie, a hybrid coined by Christian Gottfried Schütz (1747-1832), professor of poetry and rhetoric at Jena, from Medieval Latin terminus "word, expression" (see terminus) + Greek -logia "a dealing with, a speaking of" (see -logy). Related: Terminological.
Decandolle and others use the term Glossology instead of Terminology, to avoid the blemish of a word compounded of two parts taken from different languages. The convenience of treating the termination ology (and a few other parts of compounds) as not restricted to Greek combinations, is so great, that I shall venture, in these cases, to disregard this philological scruple. [William Whewell, "The Philosophy of the Inductive Sciences," 1847]
terminus (n.): 1550s, "goal, end, final point," from Latin terminus (plural termini) "end, boundary line," from PIE *ter-men-, from root *ter-, base of words meaning "peg, post, boundary, marker, goal" (source also of Sanskrit tarati "passes over, crosses over," tarantah "sea;" Hittite tarmaizzi "he limits;" Greek terma "boundary, end, limit;" Gothic þairh, Old English þurh "through;" Old English þyrel "hole;" Old Norse þrömr "edge, chip, splinter").

In ancient Rome, Terminus was the name of the deity who presided over boundaries and landmarks, focus of the important Roman festival of Terminalia (held Feb. 23, the end of the old Roman year). Meaning "either end of a transportation line" is first recorded 1836.
termite (n.): 1849, back-formation from plural form termites (1781), from Modern Latin termites (three syllables), plural of termes (genitive termitis), a special use of Late Latin termes "woodworm, white ant," altered (by influence of Latin terere "to rub, wear, erode") from earlier Latin tarmes. Their nest is a terminarium (1863). Earlier in English known as wood ant or white ant.
terms (n.): "limiting conditions," early 14c.; see term (n.). Hence expressions such as come to terms, make terms, on any terms, etc. Meaning "standing, footing, mutual relations," as in expression on good terms (with someone), is recorded from 1540s.
tern (n.): gull-like shore bird (subfamily Sterninae), 1670s, via East Anglian dialect, from a Scandinavian source (compare Danish terne, Swedish tärna, Færoese terna) related to Old Norse þerna "tern" (also "maid-servant"), cognate with Old English stearn.
ternary (adj.): "threefold," early 15c., from Late Latin ternarius "consisting of three," from terni "three by three," from ter "thrice," which is related to tres "three" (see three).
Terpsichore (n.): the muse of the dance, Greek Terpsikhore, literally "enjoyment of dance," from terpein "to delight" (from PIE root *terp- "to satisfy;" source also of Sanskrit trpyati "takes one's fill," Lithuanian tarpstu "to thrive, prosper") + khoros "dance, chorus" (see chorus).
terpsichorean (adj.): "pertaining to dancing," 1869, literally "of Terpsichore," from Latinized form of Greek Terpsikhore, muse of dancing and dramatic chorus (see Terpsichore). Hence theatrical slang terp "stage dancer, chorus girl" (1937).
terr (n.): Rhodesian slang abbreviation of terrorist, 1976, used in reference to guerrilla fighting against white minority government.
terra (n.): Latin, literally "earth" (see terrain).
terra firma (n.): c. 1600, "part of the Italian mainland ruled by Venice," from Modern Latin terra firma, literally "firm land," from Latin terra "earth, land" (see terrain) + firma, fem. of firmus "strong, steadfast" (see firm (adj.)). Meaning "the land" (as distinct from "the sea") is first attested 1690s. Hakluyt and Sandys also used English firm (n.) to mean "the firm land, the mainland, terra firma."
terra incognita (n.): "unknown or unexplored region," 1610s, Latin, literally "unknown land," from terra (see terrain) + fem. of incognito.
terra-cotta (n.): 1722, from Italian terra cotta, literally "cooked earth," from terra "earth" (see terrain) + cotta "baked," from Latin cocta, fem. past participle of coquere (see cook (n.)). As a color name for brownish-red, attested from 1882.
terrace (n.): 1510s, "gallery, portico, balcony," later "flat, raised place for walking" (1570s), from Middle French terrace (Modern French terasse), from Old French terrasse (12c.) "platform (built on or supported by a mound of earth)," from Vulgar Latin *terracea, fem. of *terraceus "earthen, earthy," from Latin terra "earth, land" (see terrain). As a natural formation in geology, attested from 1670s. In street names, originally in reference to a row of houses along the top of a slope, but lately applied arbitrarily as a fancy name for an ordinary road. As a verb from 1610s, "to form into a terrace." Related: Terraced.
terrain (n.): 1727, "ground for training horses," from French terrain "piece of earth, ground, land," from Old French (12c.), from Vulgar Latin *terranum, from Latin terrenum "land, ground," noun use of neuter of terrenus "of earth, earthly," from terra "earth, land," literally "dry land" (as opposed to "sea"); from PIE root *ters- "to dry" (source also of Sanskrit tarsayati "dries up," Avestan tarshu- "dry, solid," Greek teresesthai "to become or be dry," Latin torrere "dry up, parch," Gothic þaursus "dry, barren," Old High German thurri, German dürr, Old English þyrre "dry;" Old English þurstig "thirsty"). Meaning "tract of country, considered with regard to its natural features" first attested 1766.
terran (adj.): "of or pertaining to the planet Earth," 1881, in science fiction writing, from Latin terra (see terrain). Also used as a noun meaning "inhabitant of the Earth" (1953). An earlier form, terrene was used in Middle English in sense of "belonging to this world, earthly, secular, temporal" (c. 1300), later, "of the Earth as a planet" (1630s).
terrapin (n.): North American turtle, 1670s, earlier torope (1610s), from an Algonquian source (such as Abenaki turepe, Munsee (Delaware) tolpew "turtle"). Subsequently extended to allied species in South America, East Indies, China, North Africa.
terraqueous (adj.): "consisting of both land and water," 1650s, from comb. form of Latin terra "earth" (see terrain) + aqueous.
terrarium (n.): 1877, from Latin terra "land" (see terrain) + -arium, abstracted from aquarium.
terrazzo (n.): type of flooring material, 1893, from Italian terrazzo "terrace, balcony" (see terrace).
terrene (adj.): "earthly, terrestrial, of or pertaining to the earth," c. 1300, from Anglo-French terreine, Old French terrien, from Latin terrenus "on the earth, earthly," from terra "earth" (see terrain).
terrestrial (adj.): late 14c., "of or pertaining to the earth," with + -al (1) + from Latin terrestris "earthly, of the earth, on land," from terra "earth" (see terrain). Originally opposed to celestial; natural history sense of "living on land" is attested from 1630s. The noun meaning "a human being, a mortal" is recorded from 1590s.
terrible (adj.): late 14c., "causing terror, awe, or dread; frightful," from Old French terrible (12c.), from Latin terribilis "frightful," from terrere "fill with fear," from PIE root *tres- "to tremble" (source also of Sanskrit trasati "trembles," Avestan tarshta "feared, revered," Greek treëin "to tremble," Lithuanian trišeti "to tremble," Old Church Slavonic treso "I shake," Middle Irish tarrach "timid"). Weakened sense of "very bad, awful" is first attested 1590s.
terribly (adv.): "dreadfully, so as to cause terror, in a horrible manner," mid-15c., from terrible + -ly (2). In the sense of "extremely" it is first recorded 1833; in the sense of "extremely badly" it dates from 1930.
terrier (n.): kind of dog, early 15c., from Old French chien terrier "terrier dog," literally "earth dog," from Medieval Latin terrarius "of earth," from Latin terra "earth" (see terrain). So called because the dogs pursue their quarry (foxes, badgers, etc.) into their burrows.
terrific (adj.): 1660s, "frightening," from Latin terrificus "causing terror or fear, frightful," from terrere "fill with fear" (see terrible) + root of facere "to make" (see factitious). Weakened sensed of "very great, severe" (as in terrific headache) appeared 1809; inverted colloquial sense of "excellent" began 1888. Related: Terrifically.
terrify (v.): 1570s, from Latin terrificare "to frighten, make afraid," from terrificus "causing terror" (see terrific). Related: Terrified; terrifying.
terrine (n.): earthenware dish, 1706, obsolete original form of tureen.
territorial (adj.): 1620s, "of or pertaining to a territory," from Late Latin territorialis, from territorium (see territory). In reference to British regiments, from 1881. In reference to an area defended by an animal, from 1920. Territorial waters is from 1841. Territorial army "British home defense" is from 1908. Territorial imperative "animal need to claim and defend territory" is from 1966.
territoriality (n.): "possession and control of territory," 1839, as a concept in international law, from territorial + -ity. From 1941 in reference to animal behavior.
territory (n.): late 14c., "land under the jurisdiction of a town, state, etc.," probably from Latin territorium "land around a town, domain, district," from terra "earth, land" (see terrain) + -orium, suffix denoting place (see -ory). Sense of "any tract of land, district, region" is first attested c. 1600. Specific U.S. sense of "organized self-governing region not yet a state" is from 1799. Of regions defended by animals from 1774.

"Since -torium is a productive suffix only after verbal stems, the rise of terri-torium is unexplained" [Michiel de Vaan, "Etymological Dictionary of Latin and the other Italic Languages"]. An alternative theory, somewhat supported by the vowels of the original Latin word, suggests derivation from terrere "to frighten" (see terrible); thus territorium would mean "a place from which people are warned off."
terror (n.): early 15c., "something that intimidates, an object of fear," from Old French terreur (14c.), from Latin terrorem (nominative terror) "great fear, dread, alarm, panic; object of fear, cause of alarm; terrible news," from terrere "fill with fear, frighten," from PIE root *tres- "to tremble" (see terrible).

From c. 1500 as "fear so great as to overwhelm the mind." Meaning "quality of causing dread" is attested from 1520s. Sense of "a person fancied as a source of terror" (often with deliberate exaggeration, as of a naughty child) is recorded from 1883. Terror bombing first recorded 1941, with reference to German air attack on Rotterdam. Terror-stricken is from 1831. The Reign of Terror in French history (March 1793-July 1794) was the period when the nation was ruled by a faction whose leaders made policy of killing by execution anyone deemed an impediment to their measures; so called in English from 1801. Old English words for "terror" included broga and egesa.
terrorise (v.): chiefly British English spelling of terrorize (q.v.); for suffix, see -ize. Related: Terrorised; terrorising.
terrorism (n.): 1795, in specific sense of "government intimidation during the Reign of Terror in France" (March 1793-July 1794), from French terrorisme, from Latin terror (see terror).
If the basis of a popular government in peacetime is virtue, its basis in a time of revolution is virtue and terror -- virtue, without which terror would be barbaric; and terror, without which virtue would be impotent. [Robespierre, speech in French National Convention, 1794]
General sense of "systematic use of terror as a policy" is first recorded in English 1798 (in reference to the Irish Rebellion of that year). At one time, a word for a certain kind of mass-destruction terrorism was dynamitism (1883); and during World War I frightfulness (translating German Schrecklichkeit) was used in Britain for "deliberate policy of terrorizing enemy non-combatants."
terrorist (n.): in the modern sense, 1944, especially in reference to Jewish tactics against the British in Palestine -- earlier it was used of extremist revolutionaries in Russia who attempted to demoralize the government by terror (1866); and Jacobins during the French Revolution (1795) -- from French terroriste; see terror + -ist (also see terrorism).
The term now usually refers to a member of a clandestine or expatriate organization aiming to coerce an established government by acts of violence against it or its subjects. [OED]
The tendency of one party's terrorist to be another's guerilla or freedom fighter was noted in reference to the British action in Cyprus (1956) and the war in Rhodesia (1973). The word terrorist has been applied, at least retroactively, to the Maquis resistance in occupied France in World War II (as in in the "Spectator," Oct. 20, 1979).
terroristic (adj.): 1842, from terrorist + -ic. Related: Terroristical.
terrorize (v.): "coerce or deter by terror," 1823, from terror + -ize (also see terrorism). Related: Terrorized; terrorizing; terrorization.
terry (n.): "loop raised in pile-weaving, left uncut," 1784, of uncertain origin, possibly an alteration of French tiré "drawn," from past participle of tirer "draw out" (compare German gezogener Sammet "drawn velvet").
terse (adj.): 1590s (implied in tersely), "clean-cut, burnished, neat," from French ters "clean," and directly from Latin tersus "wiped off, clean, neat," from past participle of tergere "to rub, polish, wipe." Sense of "concise or pithy in style or language" is from 1777, which led to a general sense of "neatly concise." The pejorative meaning "brusque" is a fairly recent development. Related: Terseness.
tertiary (adj.): 1650s, "of the third order, rank, degree, etc.," from Latin tertiarius "of or pertaining to a third," from tertius "third, a third," from root of tres "three" (see three). The geological sense (with capital T-) of "era after the Mesozoic" (which formerly was called the Secondary) is attested from 1794, after Italian terziari, used in this sense 1760 by Italian geologist Giovanni Arduino (1714-1795).
tertium quid (n.): something indeterminate between two other things, 1724, Latin, literally "third something," from tertius "third, a third," from the root of tres "three" (see three). A loan-translation of Greek triton ti (Plato), used in alchemy for "unidentified element present in a combination of two known ones." The Latin word also figures in phrases tertium non datur "no third possibility exists," and tertius gaudens "a third party that benefits from conflict between the other two."
terza rima (n.): 1819, Italian, literally "third rhyme." Dante's measure: a-b-a-b-c-b-c-d-c-, etc.
tesla (n.): "unit of magnetic flux density," 1960, from Nikola Tesla (1856-1943), Croatian-born U.S. engineer. Tesla coil is attested from 1896.
tessellated (adj.): 1690s, from Late Latin tessellatus "made of small square stones or tiles," past participle of tesselare, from tessella "small square stone or tile," diminutive of tessera "a cube or square of stone or wood," perhaps from Greek tessera, neuter of tesseres, Ionic variant of tessares "four" (see four), in reference to four corners. Related: Tessellate (v.), a 1791 back-formation (from 1826 as an adjective, 1909 as a noun); tessellating.
tessellation (n.): "minute arrangement of parts or colors," 1650s, noun of action from Late Latin tessellatus (see tessellated).