What is the X in X-mas?
late 14c., from Anglo-French progenitour (mid-14c.), Old French progeniteur (14c.) and directly from Latin progenitor "ancestor, the founder of a family," agent noun from progenitus, past participle of progignere (see progeny). Related: Progenitive; progenital; progenitrix (c.1600).
progenitor pro·gen·i·tor (prō-jěn'ĭ-tər)
A direct ancestor.
An originator of a line of descent.