also moustache (chiefly British), "the hair that grows upon the upper lip of men," 1580s, from French moustache (15c.), from Italian mostaccio, from Medieval Greek moustakion, diminutive of Doric mystax (genitive mystakos) "upper lip, mustache," related to mastax "jaws, mouth," literally "that with which one chews" (perhaps from PIE root *mendh- "to chew;" see mandible), but Beekes says this whole group of Greek words may be of Pre-Greek origin.
Borrowed earlier (1550s) as mostacchi, from the Italian word or its Spanish derivative mostacho. The plural form of this, mustachios, lingers in English (the mustache sometimes was considered as the hair on either side of the lip, hence the use of the plural form). Slang shortening stache attested from 1985. Old English had cenep "mustache," which is related to cnafa "boy" (see knave). Mustache-cup, one with a fixed cover over part of its top, allowing one to drink without dipping the mustache, is by 1868.