was the link to Quinion? http://www.quinion.com/words/articles/nineyards.htm
you don't like his non-answer? there are some mysteries in our language and it would appear that this is one.

Quinion: If you're hoping for a definitive answer, you'd better buy a crystal ball. I have to say straight away this is one of the great unsolved mysteries of modern etymology, for which many seek the truth and almost as many find explanations, but hardly anyone has a clue. What we do know is that the phrase is recorded from the 1960s, is an Americanism (it's nothing like so well known in Britain, for example), and has the meaning of "everything; all of it; the whole lot; the works". But there are no leads anyone can discover to a reasonable idea of where it came from.