What is the X in X-mas?
"pertaining to Catalonia," also as a noun, "person from Catalonia," late 15c., from the indigenous name, which is of Celtic origin and probably means "chiefs of battle." As a noun meaning "a Catalan," Middle English used Catelaner (mid-14c.), Catellain (early 15c., from French). As a language name in English by 1792. Related: Catalonian (1707).