What is the X in X-mas?
1550s, "the service of the Holy Eucharist," from Middle French liturgie or directly from Late Latin/Medieval Latin liturgia "public service, public worship," from Greek leitourgia "a liturgy; public duty, ministration, ministry," from leitourgos "one who performs a public ceremony or service, public servant," from leito- "public" (from laos "people;" cf. leiton "public hall," leite "priestess;" see lay (adj.)) + -ergos "that works," from ergon "work" (see urge (v.)). Meaning "collective formulas for the conduct of divine service in Christian churches" is from 1590s.