Originally Posted by
T8191
"Xmas" springs to mind as another "X" abbreviation, which I personally abhor
X is an abbreviation for Christ. I don't think that's the same reason as Pax.
The Oxford English Dictionary (OED) and the OED Supplement have cited usages of "X-" or "Xp-" for "Christ-" as early as 1485
I can't provide a reason for pax, other than it's easier/clearer than pas, which looks like a typo. But it's entrenched in the
lexicon.