What is the X in X-mas?
late 14c., "quality of being new," also "a new manner or fashion, an innovation; something new or unusual," from Old French noveleté "newness, innovation, change; news, new fashion" (Modern French nouveauté), from novel "new" (see novel (adj.)). Meaning "newness" is attested from late 14c.; sense of "useless but amusing object" is attested from 1901 (e.g. novelty shop, 1973).