In that case, I don't understand the point you were trying to make by saying "Except Christians were the first ones to replace Christ's name with X, the first letter in the Greek Χριστός."

It sounded like you were trying to disagree with my assertion that Xtian had a certain rhetorical intent, but you did it by bringing in a completely different rhetorical construct.

I do know the origins of the X abbreviation.