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.

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

"in reference to organizations or forces analogous or auxiliary to that of military units but not professional," 1935, from para- (1) + military. In early use often in reference to the S.A. and S.S. of Nazi Germany.

1841, "military spirit, addiction to war or military practice," from French militarisme, from militaire "military" (see military); also see -ism. By 1864 in reference to nations or peoples, "predominance of the military class, maintenance of national power by means of standing armies."

1620s, of persons, "to serve as a soldier" (now rare), from Latin militatum, past participle of militare "serve as a soldier," from miles "soldier" (see military (adj.)). The sense developed via "to be in conflict with, be at variance" to "be evidence" for or against, "have weight or force in determining anything" (1640s). Related: Militated; militating; militation.

1580s, "system of military discipline," from Latin militia "military service, warfare," from miles "soldier" (see military (adj.)). The sense of "citizen army" (as distinct from professional soldiers) is first recorded 1690s, perhaps from a sense in French cognate milice. Historically, the Anglo-Saxon forces that resisted the Vikings were militias, raised by counties. In U.S. history, by 1777 as "the whole body of men declared by law amenable to military service, without enlistment, whether armed and drilled or not" [Century Dictionary]. In early 19c. they were under control of the states, enrolled and drilled according to military law but not as regular soldiers, and called out periodically for drill and exercise and in emergency for actual service.

"military attendant who carries orders," 1781, short for orderly corporal, etc. Extended 1809 to an attendant at a hospital (originally a military hospital) charged with keeping things clean and in order, from orderly (adj.) in the military sense of "of or pertaining to communication or execution of orders" (1723).

"military helicopter for taking wounded soldiers to a hospital," 1966, U.S. military, formed from elements of medical evacuation.