What is the X in X-mas?
1530s, in the Roman historical sense, from Middle French ovation or directly from Latin ovationem (nominative ovatio) "a triumph, rejoicing," noun of action from past participle stem of ovare "exult, rejoice, triumph," probably imitative of a shout (cf. Greek euazein "to utter cries of joy"). In Roman history, a lesser triumph, granted to a commander for achievements insufficient to entitle him to a triumph proper. Figurative sense of "burst of enthusiastic applause from a crowd" is first attested 1831.