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.