What is the X in X-mas?
c.1600 (n.); 1610s (adj.), from Latin Iberia, ancient name of the Spanish peninsula, from Greek Iberes "Celtic people of Spain;" also the name given to an Asiatic people near the Caucasus. Of unknown origin in both uses, but the word as applied in Spain is believed to be related to the River Ebro. The earliest English reference is to the Caucasians; in reference to Spain and Portugal it dates from 1610s.