Don't Be Thick

Flicking through the channels, a caught a bit of an old sitcom--The Partridge Family, believe it or not--and the main characters were going through a series of problems. At the end, one of them said "we stick together through thick and thin, and today was definitely thick."

Wait a second, I thought, which is the good one, thick or thin? I always assumed the thin times were the bad ones, when you didn't have much.  So I looked up the origin of the phrase and was surprised to find thick was bad.  It's an old English phrase about traveling, and started out as "through thicket and thin wood."

So chalk one up to the writers of the show. It's still pretty crappy, but they knew their idioms.