Found it...pretty fast too

Well, that letter may look like an "X" and walk like an "X" and quack like an "X," but it isn't an "X." That's the Greek letter "chi" which is pronounced about like "ch" was in Old English ... which is to say, about how it's pronounced in German today, or in a few imported words, like "Christ" or "Christmas," for example.

"X" (as in chi) was used as an abbreviation for Christ from early times, perhaps initially as a camouflage for the religion. It was the first letter of the word Christos (meaning "the anointed one," e.g., the Messiah) and fortuitously was cross-shaped, so there seemed to be some symbolism or double meaning. It's been used as a scholarly and not-so-scholarly abbreviation since.

http://www.straightdope.com/mailbag/mxmas.html
MudFu Reviewed by MudFu on . What do you think? There has been many reports on the News latly of upset Christians who think Christmas is being ruined. Instead of Merry Christmas on cards and on T.V it has been replaced with Season Greetings or Happy Holidays. Christian's say that it shouldn't be this way and that it is being unfair to them. Now the funny thing about this is that their are more hoildays during this time then Christmas. The Jewish people have their holiday comming up and I don't think I have EVER seen on T.v an ad saying Happy Rating: 5