From: utzoo!decvax!harpo!npoiv!npois!houxm!houxa!houxb!houxq!houxo!mts
Newsgroups: net.followup
Title: re: X in Xmas
Article-I.D.: houxo.134
Posted: Tue Jan 11 09:21:59 1983
Received: Wed Jan 12 06:31:33 1983

You are right. The "X" is from the initial Greek letter
of Christ's name(Xristos).