Pet form of John, also used as an independent given name from the 16th century onwards. In the United States it is occasionally also used as a girl's name. Famous bearers include the American country singer Johnny Cash (1932–2003) and the film actor Johnny Depp (b. 1963).
Italian, Spanish, and Portuguese: from barbo ‘barbel’ (the fish), hence a metonymic occupational name for a fisherman or possibly a nickname for a man with a sparse beard, the fish being distinguished by beardlike growths on either side of its mouth.