Origin: 1560–70; (< Middle French ) < Italian zan(n)i (later zanno) a servant character in the commedia dell’arte, perhaps orig. the character's name, the Upper Italian form of Tuscan Gianni, for Giovanni John
comic performer, 1588, from Fr. zani, from It. zani, zanni "a zany, clown," originally Zanni, Venetian dial. variant of Gianni, pet form of Giovanni "John." A stock character in old comedies, he aped the principal actors. The adj. is attested by 1869, from the noun.