1530s, "a cover for the face (with openings for the eyes and mouth), a false face," from Middle French masque "covering to hide or guard the face" (16c.), from Italian maschera, from Medieval Latin masca "mask, specter, nightmare," a word of uncertain origin.
It is perhaps from Arabic maskharah "buffoon, mockery," from sakhira "be mocked, ridiculed." Or it may come via Provençal mascarar, Catalan mascarar, Old French mascurer "to black (the face)," which is perhaps from a Germanic source akin to English mesh (q.v.). But it may be a Provençal word originally: Compare Occitan mascara "to blacken, darken," derived from mask- "black," which is held to be from a pre-Indo-European language, and Old Occitan masco "witch," surviving in dialects; in Beziers it means "dark cloud before the rain comes." [See Walther von Wartburg, "Französisches Etymologisches Wörterbuch: Eine Darstellung galloromanischen sprachschatzes"].
Figurative meaning "anything used or practiced for disguise or concealment" is by 1570s.