X is actually the Greek letter “chi.” Chi is the first letter in the word Χριστός (Christos ), which means “Christ.” X has been an acceptable shortening of the word “Christ” for nearly a thousand years, way before modern day Christians began taking offense at its use.
In fact, The Greek letters “X” (Chi) and “p” (Rho) melded together was once a very common symbol signifying Christ and was called the Chi-Rho. The Chi-Rho was also used by scribes to mark a passage, implying that it was “good”.
You can see here Angel Gabriel represented with the letter "X" on his shield also Gabriel is considered as the messenger of God.
You can see here Angel Gabriel represented with the letter "X" on his shield also Gabriel is considered as the messenger of God.