It is a popular refrain among “No Information Voters” that the word Xmas was invented to take Christ out of Christmas. As usual, the information they receive is inaccurate, and I will try to assist.
In the original Greek, Christ is written as Χριστός (more accurately it is Christos, meaning “anointed”). As you should know, the New Testament was all written in Greek, the administrative language of the Roman Empire.
The first two letters are not XP as we use today, but Chi and Rho. Pictured below is the Labarum, a Chi and Rho superimposed on each other, which was the symbol for the Early Christian Church. This is the actually “cross” that Constantine added to his banners and shields before he became the first Christian Emperor. The cross symbol we use today was not officially adapted until later in the 4th century.
As an aside, Greek is the same reason people have a fish symbol on the back of their cars. In Greek, ‘fish” is written as ἰχθύς or ichthys in our spelling. It happened to also to be an acronym for Ίησοῦς Χριστός, Θεοῦ Υἱός, Σωτήρ” or “Iēsous Christos, Theou Yios, Sōtēr” or as we would say “Jesus Christ, Son of God, Saviour”. It was also easy to draw, being one line that sweeps back on itself.
You have to understand that for most of the history of Christianity, books had to be handwritten, and scribes and clerks used abbreviations or code letters, similar to shorthand, to save time. “X” or Chi became a common abbreviation for “Christ” over 1000 years ago, and perhaps longer. It has even been used in other situations abbreviating the same letters, such as Xopher for Christopher.
The use of Xmas is fairly common in books, pamphlets, and even advertising for the last 200 years.
So, the use of Xmas to abbreviate the Christ Mass is an old tradition, and you should feel free to use it whenever you wish.