The term User Experience goes back to Don Norman sometime in the early 90s.
But where did the abbreviation UX, rather than UE, come from?
I'm guessing that it was influenced by the release of Windows XP ("short for Experience") which came out in late 2001).
I came across a copy of the UPA Magazine from Winter 2002 which is called 'User Experience' and a page in this gives "The UX Book Selection" - so UX rather than UE was being used then.
Can anyone provide some earlier history or references?