What is the X in X-mas?
masc. personal name, in medieval lore the name of one of Charlemagne's peers, friend of Roland, from French Olivier, from Middle Low German Alfihar, literally "elf-host, elf-army," from alf "elf" (see elf) + hari "host, army" (see harry (v.)). Cognate with Anglo-Saxon name Ælfhere. Form influenced in Old French by olivier "olive tree."