Why is there supposed to be a pot of gold at the end of the rainbow?

Dear Cecil: Who in the world dreamed up the idea that there’s a pot of gold at the end of the rainbow? Anonymous, Los Angeles

Cecil replies:

Who knows? The expression has been proverbial at least since 1836, and the idea of chasing rainbows period goes back a lot earlier than that. The catch, of course, is that you can’t get to the end of the rainbow, owing to the fact that it’s an optical effect dependent on the relative orientation of the sun, you, and a suitable collection of airborne water droplets. If you’re not directly between the droplets and the sun, no bow. If you spot a bow and try to chase it, it simply recedes before you until the angles don’t line up anymore, at which point it disappears.

Rainbows are strictly in the eye of the beholder. You may see a small local bow created by the mist from a squirting garden hose, but somebody on the other side of the hose will see nothing. Not only can’t you get to the end of the rainbow, you can’t even sidle around it — no matter what you do, the rainbow always appears to face straight toward you. As a result, chasing rainbows has come to symbolize, depending on your degree of cynicism, either pursuing a fool’s errand or dreaming the impossible dream.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.