why is christmas called xmas

The term "Xmas" has been used as a shortened way of saying "Christmas" since at least the 16th century. It is derived from the Greek word for Christ, which is "Xristos", and was originally used to save space in writings and printed materials. Over time, the use of "Xmas" has become more common and accepted, although some people still prefer to use the full word "Christmas" for religious or cultural reasons.