derogatory for "Italian," 1912, Amer.Eng. slang, apparently from southern It. dialect
guappo "dandy, dude, stud," a greeting among male Neapolitans, said to be from Sp.
guapo "bold, dandy," which is from L.
vappa "sour wine," also "worthless fellow;" related to
vapidus (see
vapid).