1580s, from Fr. moustache, from It. mostaccio, from Medieval Gk. moustakion, dim. of Doric mystax (gen. mystakos) "upper lip, mustache," related to mastax "jaws, mouth," lit. "that with which one chews," from PIE base *mnto- "mouth" (see mouth
). Borrowed earlier (1550s) as
mostacchi, from the It. word or its Sp. derivative mostacho. The plural form of this, mustachios, lingers in English. Dutch slang has a useful noun, de befborstel, to refer to the mustache specifically as a tool for stimulating the clitoris; probably from beffen "to stimulate the clitoris with the tongue."