"military dwelling place," 1590s, from quarter (n.1) in sense of "portion of a town." As "part of an American plantation where the slaves live," from 1724. The military sense seems to be also the source of quartermaster and it might be behind the phrase give quarter "spare from immediate death" (1610s, often in the negative), on the notion of "provide a prisoner with shelter;" see quarter (n.2).

"soldiers generally," 1757, from military (adj.); commonly only with the definite article. Earlier, "a military man" (1736).

mid-15c., militari, "pertaining to or befitting soldiers; used, done, or brought about by soldiers," from Old French militaire (14c.) and directly from Latin militaris "of soldiers or war, of military service, warlike," from miles (genitive militis) "soldier," a word of unknown origin.

Perhaps ultimately from Etruscan, or else meaning "one who marches in a troop," and thus connected to Sanskrit melah "assembly," Greek homilos "assembled crowd, throng." De Vaan writes, "It is tempting to connect mīlia [pl.] 'thousand(s)', hence *mīli-it- 'who goes with/by the thousand' ...." Related: Militarily. Old English had militisc, from Latin.

Military police is from 1827. Military age, at which one becomes liable to military service, is by 1737. Military-industrial complex was coined 1961 in the farewell speech of U.S. president Dwight D. Eisenhower.

1722, originally nautical, also close-fights, "bulkheads fore and aft for men to stand behind in close engagements to fire on the enemy," it reflects the confusion of close (v.) and close (adj.); "now understood of proximity, but orig. 'closed' space on ship-board where last stand could be made against boarders" [Weekley]. Compare also closed-minded (1880s), a variant of close-minded, as if "shut" rather than "tight," also closed-fisted, occasional variant of close-fisted "stingy."

"station when on duty, a fixed position or place," 1590s, from French poste "place where one is stationed," also, "station for post horses" (16c.), from Italian posto "post, station," from Vulgar Latin *postum, from Latin positum, neuter past participle of ponere "to place, to put" (see position (n.)). Earliest sense in English was military; the meaning "job, position, position" is attested by 1690s. The military meaning "fort, permanent quarters for troops" is by 1703.