Words of warning:

This is one of the most fun, interesting topics I know of to talk about. Each new phrase derivation is a joyful little discovery, and one generally goes around sharing it with one's friends for days afterward, But you have to be careful what source you found the history in. "The whole nine yards" is an expression that has been the bane of folklorists and phraseologists for years...almost every field of human endeavor claims to be at its root, and there are actually no clearly substantiated histories for it. Another one you often hear is that "mind your p's and q's" came from tavern keepers who marked down how many Pints or Quarts a toper drank; that's a cute story, but a false one, as there is a lot more documentation for the phrase having come from typesetting in a print shop.(The p's and q's , since they're molded backward on a piece of type, are easy to mix up.)