IAMBUS, in the Greek and Latin prosody, a poetical foot, consisting of a short syllable followed by a long one; as in
ὅν ἄγνῳ, Δεί, μέας.
Syllaba longa brevī subjēcta vocatur iambus, as Horace expresses it; who also calls the iambus a swift, rapid foot, pes citus.
The word, according to some, took its rise from Iambus, the son of Pan and Echo, who invented this foot; or, perhaps, who only used sharp biting expressions to Ceres, when afflicted for the death of Proserpine. Others rather derive it from the Greek ἰσ, venenum, "poison;" or from ἰσάδω, maledico, "I rail, or revile;" because the verses composed of iambus's were at first only used in satire.