Sou
This was an ancient French coin, not used since the 1700s. However, the word remains in use as a general term for money, earnings, or wealth.
Why I Looked It Up
In my notes, I have the phrase “not worth a sou.” This is clearly some idiom saying that a person or thing is useless.
I can’t remember where I saw it, and I was going to delete it, when a NY Times crossword was:
Old coin of France