"I have to pee like a racehorse."

Time to veer into the world of the disgusting...

How many times did you hear this expression in high school or college? If you hung out with the same sort of people that I did--drunken fraternity guys who drank lots of cheap beer--then you heard it a lot. In case you've ever lain awake in the early morning hours wondering where the expression came from, Slate's Explainer has your answer.