WXS acronym?

I've been seeing the acronym WXS to describe XML Schema for a long time on 
this mailing list, and I have no idea where it came from. It's likely to 
confuse people since the acronym is never used on the W3C site, and it 
simply isn't the name of a schema language.

Is there a reason for not calling this language W3C XML Schema or XSDL, the 
official name and acronym for the language respectively?

Jonathan