What is the X in X-mas?
masc. proper name, common in England and Scotland by mid-12c. (Pope Gregory I sent the men who converted the English to Christianity), from Late Latin Gregorius, from Greek gregorios, a derivative of gregoros "to be watchful," from PIE root *ger- "to be awake" (cf. Sanskrit jagarti "he is awake," Avestan agarayeiti "wakes up, rouses"). At times confused with Latin gregarius (see gregarious).