What is the X in X-mas?
1580s, from earlier adjective (14c.), from Old French festival "suitable for a feast, solemn, magnificent, joyful, happy," and directly from Medieval Latin festivalis "of a church holiday" (see festivity).
day or period of time set aside to commemorate, ritually celebrate or reenact, or anticipate events or seasons-agricultural, religious, or sociocultural-that give meaning and cohesiveness to an individual and to the religious, political, or socioeconomic community. Because such days or periods generally originated in religious celebrations or ritual commemorations that usually included sacred community meals, they are called feasts or festivals.