One of my pet theories is that no idea in computing every really takes off until at least ten years after it has been first hatched. XML goes back to the Eighties. So too does Python.
Would you trace AJAX back ten years yet? Its getting there believe it or not.
Back in 1997 Jon Bosak wrote about the slogan "XML gives Java something to do". http://www.ibiblio.org/pub/sun-info/standards/xml/why/xmlapps.htm.
He was talking about client/server computing, browsers etc.