What is the X in X-mas?
c.1300, "inscription, heading," from Old French title (12c.), and in part from Old English titul, both from Latin titulus "inscription, heading," of unknown origin. Meaning "name of a book, play, etc." first recorded mid-14c. The sense of "name showing a person's rank" is first attested 1580s.
"to furnish with a title," late 14c., from title (n.). Related: Titled; titling.