"Christmas" is a shortened form of "Christ's mass". The word is recorded as Crīstesmæsse in 1038 and Cristes-messe in 1131. Crīst (genitive Crīstes) is from Greek Khrīstos (Χριστός), a translation of Hebrew Māšîaḥ (מָשִׁיחַ), "Messiah", meaning "anointed"; and mæsse is from Latin missa, the celebration of the Eucharist.

The form Christenmas was also historically used, but is now considered archaic and dialectal. The term derives from Middle English Cristenmasse, meaning "Christian mass". Xmas is an abbreviation of Christmas found particularly in print, based on the initial letter chi (Χ) in Greek Khrīstos (Χριστός), "Christ", though numerous style guides discourage its use. This abbreviation has precedent in Middle English Χρ̄es masse (where "Χρ̄" is an abbreviation for Χριστός).