“Xmas” is a controversial way to talk about Christmas these days. Many people (Christians mainly!) believe that it is a disgrace to place an “X” where “Christ” should be. “It takes Jesus out of Christmas!” they purport.
Jesus of Nazareth’s last name was not “Christ.” Christ is his office. And Christ means, “Anointed One.” In other words, he is Messiah.
In Greek, it looks like this: Χριστός
Notice the letters in the Greek alphabet, specifically the first two: Χ (Chi) & ρ (Rho). This is pictured above as an “X” with the letter “Rho” together, as an early symbol of Christianity (well before the cross–as this article makes clear).
Long before atheists, agnostics and other not-yet-Christians began using this in short form, the letter “Chi” or “X” was used as a symbol for Christ. When we say “Xmas,” we are merely coding Christ in simple one-letter terms–an abbreviation for Christ, and ultimately CHRISTmas.
Check out what R.C. Sproul wrote three years ago on this same topic.