I find it a little curious that people think that "Xmas", as written, is or could ever cheapen or belittle the meaning or importance of Christmas.
As a clearer and more concise explanation, XP (and to a lesser extent Xt) were used to signify Christ, as they the first two (or first and fifth, in the case of Xt) letters in the Greek word that means "Christ". As much of the early documentation of the christian religion was written in Greek, it became the accepted symbol of Christ. As did X.
When being written (or printed, in latter times) the symbol XP was quicker and easier to produce than "Christ". So it was used. When the process of printing became easier and cheaper, XP was dropped for the english "Christ". And so it is.
However, the XP still lives on in churches, in the form of the labarum, a symbol commonly, but not always, found on the top of depictions of Christ on the cross. So, you see, it's a symbol of your church from it's very beginning, and one that you should embrace, not fear. It isn't a "made-up" or artificial symbol.
History is pretty cool.
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