Welcome to Xian Ortiz! The derivation of Xian

The first letter in the Greek word for 'Christ' is 'chi,' and the Greek letter 'chi' is represented by a symbol similar to the letter 'X' in the modern Roman alphabet. Therefore 'Xian' is indeed perfectly legitimate abbreviation for the word 'Christian' just as 'Xmas' is also sometimes used as an abbreviation of the word 'Christmas'.