Were you like me and saw the headline as "42 idiot origins"? No, these are idioms, or figures of speech. He talks about how they don't "literally" mean what they say, but we know that "literally" doesn't mean what it says,either. John Green explains a boatload of familiar metaphors in the latest mental_floss video. -via mental_floss
Can't seem to find it anywhere.
(In my defense, I'm a bit dim-witted.)