What is the X in X-mas?
c.1400, haute, "high in one's own estimation, haughty," from Old French haut (11c.) "main, principal; proud, noble, dignified; eminent; loud; grand," literally "high," from Latin altus "high" (see old); with initial h- by influence of Frankish hoh "high." Spelling altered 16c. by influence of caught, naught, etc.