1911 Encyclopædia Britannica/Moustache

MOUSTACHE, or Mustachio, the hair worn unshaven on the upper lip (see Beard). The spelling “moustache,” now the most common in English usage, is the French form of Ital. mustachio, an adaptation of a Doric dialectical μύσταξ, upper lip, also hair on the lip; this is generally taken to be a variant of μάσταξ, jaws, mouth, connected with μάσασθαι, to chew; cf. “mastic,” chewing-gum, and “masticate,” to chew.