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."

in prosody, a foot of two syllables, the first short or unaccented, the second long or accented, 1842, from French iambe (16c.) or directly from Latin iambus "an iambic foot; an iambic poem," from Greek iambos "metrical foot of one unaccented followed by one accented syllable" (see iambic). Iambus itself was used in English in this sense from 1580s. In Greek it was said to have been first used by satiric writers.

in prosody, 1570s (n.) "a foot of two syllables, the first short or unaccented, the second long or accented;" 1580s (adj.), "pertaining to or employing iambs," from Late Latin iambicus, from Greek iambikos, from iambos "metrical foot of one unaccented followed by one accented syllable; an iambic verse or poem," traditionally said to be from iaptein "to assail, attack" (in words), literally "to put forth, send forth" (in reference to missiles, etc.), but Beekes says "doubtless of Pre-Greek origin."

The meter of invective and lampoon in classical Greek since it was first used 7c. B.C.E. by Archilochus, whose tomb, Gaetulicus says, is haunted by wasps; iambics of various length formed the bulk of all English poetry before 20c. and a great deal since. The iambic of classical Greek and Latin poetry was quantitative.

a titan, son of Uranus and Gaia; Latinized form of Greek Iapetos, which is of uncertain origin. It has been connected with biblical Japheth or with Greek iaptein "to put forth, send forth" (perhaps as "the one thrown" by Zeus into Tartaros" or "the one who throws" a spear, etc.). Beekes finds these improbable and suggests that, as the name of a pre-Olympian god, it is a Pre-Greek word.