Where did we get all these strange figures of speech we use nowadays? Those things that everyone says but don't make any sense, like, "a penny saved is a penny earned," or "you can't tell a book by its cover." What is meant by "earning" a penny, and for that matter, what is a "book"? Well, a long time ago when people weren't as modern and up-to-date as we are now, but were planning to get there some day, they sat around together making up the language. "If we're ever going to amount to anything," they said to each other, "we're going to need us some handy sayings we can throw around to fill in the gaps of conversation." This was especially important in an era before TV when there wasn't anything interesting to talk about. So they made up all those funny little phrases we still use today even though now, thank goodness, our lives are so much more interesting we really don't need to say them any more or even, when you get right down to it, talk.
In case you're interested, here's a few of these "figures of speech" and their origins. If you're not interested, there's a figure of speech involving the horse you rode in on you might want to look up.
The Whole Nine Yards
You might guess it has to do with football, but it doesn't. A whole football field is a lot bigger than nine yards; it's twelve or thirteen yards, depending on whether you're playing American-style football, or South Carolina-style. Actually, the original saying was "Hold My Nyards." It doesn't make any more sense than the way we say it now, but that's where it came from.
In the Oklahoma territory, farmers left gunpowder on the ground and sometimes even whole sticks of dynamite which they used when they were going fishing. Unsuspecting horses would graze and sometimes eat the explosives. This made looking into the mouth of any horse, not just a gift horse, very dangerous because, well, BOOM! This also made it dangerous looking a gift-horse in the butt-hole, but for some reason there wasn't a saying about that.
A Stitch in Time Saves Nine
There's a funny story associated with the origin of this saying involving Benjamin Franklin, Thomas Jefferson, and a Tory sympathizer named Jacob Mutts. Unfortunately, I can't remember it.
A Watched Pot Never Boils
At first glance, this doesn't even make sense. Of course a watched pot boils, just the same as any other pot, as anyone who's ever watched a boiling pot can attest. The original saying is "A boiled watch never tocks," which is why people don't boil watches any more.