Xmas is a common abbreviation of the word Christmas . It and variants such as Xtemass, originated as handwriting abbreviations . The "-mas" part is from the Latin-derived Old English word for Mass, while the "X" comes from the Greek letter Chi, which is the first letter of the Greek word Χριστός which comes into English as "Christ".
There is a common misconception that the word Xmas stems from a secular attempt to remove the religious tradition from Christmas by taking the "Christ" out of "Christmas", but its use dates back to the 16th century.
I must admit that I use Xmas alot ,purely as what it is meant for ..an abbreviation .