[kris-muhs or, often, eks-muhs] Christmas.
The abbreviation Xmas for Christmas dates from the mid 16th century. The X is the Greek letter chi, the initial in the word Χριστός ( Christos ) “Christ.” In spite of a long and respectable history, today Xmas is offensive to many, perhaps because of its associations with advertising. It is not used in formal writing.
I've found myself growing more and more bothered by the usage of "Xmas". I don't think that most people that say "xmas" are aware of its greek origin. But then again, does it really matter?
I think i need to be bothered less by this.