Etymology
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terminus (n.)

1550s, "goal, end, final point," from Latin terminus (plural termini) "an end, a limit, boundary line," from PIE *ter-men- "peg, post," from root *ter-, base of words meaning "peg, post; boundary, marker, goal" (source also of Sanskrit tarati "passes over, crosses over," tarantah "sea;" Hittite tarma- "peg, nail," tarmaizzi "he limits;" Greek terma "boundary, end-point, limit," termon "border;" Gothic þairh, Old English þurh "through;" Old English þyrel "hole;" Old Norse þrömr "edge, chip, splinter"). "The Hittite noun and the usage in Latin suggest that the PIE word denoted a concrete object which came to refer to a boundary-stone." [de Vaan]

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). The meaning "either end of a transportation line" is first recorded 1836.

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interminate (adj.)
1530s, from Latin interminatus "unbounded, endless," from in- "not" (see in- (1)) + terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line" (see terminus).
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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.
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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).
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interminable (adj.)
late 14c., from Old French interminable (14c.) or directly from Late Latin interminabilis "endless," from in- "not" (see in- (1)) + terminabilis, from terminare "to limit, set bounds, end" (see terminus (adj.)). Related: Interminably.
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terminal (adj.)
mid-15c., "relating to or marking boundaries," from Latin terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line" (see terminus). Meaning "fatal" (terminal illness) is first recorded 1891. Sense of "situated at the extreme end" (of something) is from 1805. Slang meaning "extreme" first recorded 1983. Related: Termninally.
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conterminous (adj.)

"having the same limit, touching at the boundary," 1670s, from Latin conterminus "bordering upon, having a common boundary," from assimilated form of com "together, with" (see con-) + terminus "end, boundary line" (see terminus). Related: Conterminously; conterminousness.

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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.
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determinant 

c. 1600 (adj.), "serving to determine;" 1680s (n.), "that which fixes, defines, or establishes (something);" from Latin determinantem (nominative determinans), present participle of determinare "to enclose, bound, set limits to," from de "off" (see de-) + terminare "to mark the end or boundary," from terminus "end, limit" (see terminus).

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determinable (adj.)

c. 1400, "definite;" mid-15c., in law, "capable of being decided or settled;" from Old French determinable, from Late Latin determinabilis "that has an end," from stem of Latin determinare "to enclose, bound, set limits to," from de "off" (see de-) + terminare "to mark the end or boundary," from terminus "end, limit" (see terminus). Meaning "capable of being ascertained" is from 1650s. Related: Determinability.

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