iamb

noun Prosody.

1. a foot of two syllables, a short followed by a long in quantitative meter, or an unstressed followed by a stressed in accentual meter, as in Come live / with me / and be / my love.

noun plural iambs, iambi (aɪˈæmbaɪ) or iambuses prosody

1. a metrical foot consisting of two syllables, a short one followed by a long one (◡ –)
2. a line of verse of such feet

n.

1842, from French iambe (16c.), from Latin iambus, from Greek iambos (see iambic). Iambus itself was used in English in this sense in 1580s.