Crossword Wisdom

One of today’s crosswords had a clever quip as part of its solution that (at least for me) is a new one:

A flashlight is a case for holding dead batteries.

Can you cite some neat things you have learned from working crosswords or other word puzzles?

I guess I never would have known what an etui is were it not for puzzles. I may even have one for all I know, but I never would know to call it that.

A long time ago Will Weng taught me that a five-sided brass container was a pentagon