Oh, look at the big brain on Spoo. I swear, send a gunship-killer-turned-pressure-suit-pressure-breathing-prima-donna to school, and he ends up in a velvet smoking jacket with a pipe in his mouth, explaining Greek literature to me. YGBSM.
And, the Greek letter Chi (X) is, well,... Greek. According to my Greek speaking concubine, Christ in Greek is Χριστός. I'm not going to argue with you, as my knuckle-dragging IQ has no knowledge of such things. X or XP is obviously a crude abbreviation on the word. But an X and a P have little in common with Chi and Rho. Because we speak English here. And in English, X is a rating given to various movies, and XP is a rating given to orientation flyers that jump into the back of my jet. I've never read the Bible in Greek (I'm guessing you have, so you can discuss it with your Bohemian buddies at the local Chai Tea shop?), but I'm willing to bet that the New Testament Greeks said nothing about movies and jet sorties.
Therefore, I revert back to my first supposition: the writter is lazy, despite his exhuberant letter on SNAPs.
Additionally, I know of no neckless, sloping-forehead (yes, I said "head",... get over it) fighter/attack/recce pilot that would piece together your X=Christ connection. Most military pilots on this site don't even know that the Greeks make baklava, have fuzzy balls on their military shoes, or fly F-16's,... much less that they wrote portions of the Bible in that language.
So Spoo, what's next?? Will you educate us in the finer points of Aramaic?
And to think you've become this. I weep.