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.
late 14c., "the highest faculty of the mind, capacity for comprehending general truths;" c. 1400, "faculty of understanding, comprehension," from Old French intelligence (12c.) and directly from Latin intelligentia, intellegentia "understanding, knowledge, power of discerning; art, skill, taste," from intelligentem (nominative intelligens) "discerning, appreciative," present participle of intelligere "to understand, comprehend, come to know," from assimilated form of inter "between" (see inter-) + legere "choose, pick out, read," from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')."
Meaning "superior understanding, sagacity, quality of being intelligent" is from early 15c. Sense of "information received or imparted, news" first recorded mid-15c., especially "secret information from spies" (1580s). Meaning "a being endowed with understanding or intelligence" is late 14c. Intelligence quotient first recorded 1921 (see I.Q.).
"soldiers generally," 1757, from military (adj.); commonly only with the definite article. Earlier, "a military man" (1736).
1939, from abbreviation of Military Intelligence, followed by the department number.
"intellect, intelligence," 1820, from Greek noēsis "intelligence, thought," from noein "to see, perceive, have mental perception," from noos "mind, thought" which is of uncertain origin.
"the intellectual class collectively," 1905, from Russian intelligyentsiya, from Latin intelligentia "intelligence" (see intelligence). Perhaps via Italian intelligenzia.
1922, abbreviation of intelligence quotient, a 1921 translation of German Intelligenz-quotient, coined 1912 by German psychologist William L. Stern.
Intelligence is a general capacity of an individual consciously to adjust his thinking to new requirements: it is general mental adaptability to new problems and conditions of life. [Stern, "The Psychological Methods of Testing Intelligence," 1914]
Earlier, i.q. was an abbreviation of Latin idem quod "the same as."
1580s, "spy, informant," agent noun from intelligence. Perhaps modeled on French intelligencier or Italian intelligentiere. Meaning "bringer of news, one who conveys intelligence" is from 1630s; as a newspaper name from 1640s.
U.S. civilian espionage agency, initialism (acronym) of Central Intelligence Agency, founded 1947 as successor to the Office of Strategic Services (OSS).