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."

also a.i., by 1971, abbreviation of artificial intelligence. Earlier in 20c. it stood for artificial insemination.

also counter-intelligence, "act of preventing an enemy from obtaining secret information," 1940, from counter- + intelligence.

"the sum of the cognitive facilities (except sense or sense and imagination), the capacity for reasoning truth," late 14c. (but little used before 16c.), from Old French intellect "intellectual capacity" (13c.), and directly from Latin intellectus "discernment, a perception, understanding," noun use of past participle of intelligere "to understand, discern" (see intelligence). The Latin word was used to translate Greek nous "mind, thought, intellect" in Aristotle.

c. 1400, intellecioun "meaning, purpose;" mid-15c., "the understanding;" 1610s, "an act of understanding," from Old French intelleccion and directly from Medieval Latin intellectionem (nominative intellectio), noun of action from past participle stem of Latin intelligere "to understand, discern" (see intelligence).

late 14c., "grasped by the understanding" (rather than by the senses), from Old French intellectuel (13c.) and directly from Latin intellectualis "relating to the understanding," from intellectus "discernment, understanding," noun use of past participle of intelligere "to understand, discern" (see intelligence).

Sense of "characterized by a high degree of intellect" is from 1819. Meaning "appealing to or engaging the mental powers" is from 1834. Intellectual property "products of the intellect" is attested from 1845. Adjective formations in the sense "of or pertaining to the intellect" included intellective (early 15c.), intellectile (1670s).

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.

c. 1500, a back-formation from intelligence or else from Latin intelligentem (nominative intelligens), present participle of intelligere. Intelligent design, as a name for an alternative to atheistic cosmology and the theory of evolution, is from 1999. Related: Intelligently.

"the intellectual class collectively," 1905, from Russian intelligyentsiya, from Latin intelligentia "intelligence" (see intelligence). Perhaps via Italian intelligenzia.

late 14c., "able to understand, intelligent," from Latin intelligibilis, intellegibilis "that can understand; that can be understood," from intellegere "to understand, come to know" (see intelligence). In Middle English also "to be grasped by the intellect" (rather than the senses). In English, sense of "capable of being understood, that can be understood" first recorded c. 1600. Related: Intelligibly.