A couple days ago there was this interesting exchange on the xml-dev list:
Elliotte Rusty Harold wrote:
> The X stands for eXtensible.
Tim Bray (editor of the XML specification) responded:
> Elliotte, hang your head in shame, and write on the chalkboard 10 ** 10 times:
> XML stands for Extensible Markup Language
> The X is for the first syllable of Extensible
> eXtensible is a spelling error.