“Christ mass” is the mass of Christ … It’s the name of a religious festival in Christianity celebrating the birth of Jesus Christ.
The Christians hold this festival at a time of year when many other religions also have their own festivals.
The legal Christmas holidays is a secular vacation-time where people of many nationalities and creeds celebrate family, community, and good cheer in a giving and supportive spirit.
(Supported by a commercial orgy of consumerism.)
Note: a “mass” (also spelled “mas”) is a special service in Roman Catholicism (and some others) which culminates in “Holy Communion” where adherents symbolically eat their God. Technically a Christmas should include this to be a “mass”. HOwever there is no reason not to take the mas also symbolically.
Christos means “anointed”, which is essentially the same thing as “consecrated” or “made sacred”.
Thus, Christmas means “anointed mass”. As indicated by its translation, it celebrates the family or church as a special part of the larger whole. Although Christos’ birthday is not thought to have been on the winter solstice, tagging the holiday onto the end of Rome’s Saturnalia made it convenient for early Christian cults to keep their holiday safe from persecution by the Empire.