Raining cats and dogs

So what is the origin of the phrase "The whole nine yards" anyway? What about "The real McCoy" or "Scot-free"? You can find the real deal here. The Phrase Finder has a lot of other interesting information such as popular misquotations and other meanings and origins of common English idioms. Note though that the purpose of this information is to learn how to avoid saying these things. Or as Sam Levenson said,

"It's so simple to be wise. Just think of something stupid to say and say the opposite."