Other forms: billfolds
A billfold is a slim wallet meant to hold paper money and a few cards. You might keep your billfold in the back pocket of your jeans.
There isn't much difference between a wallet and a billfold: typically, a billfold is thinner and has fewer slots for holding cards. Billfolds are most often made of leather and fit neatly in a pocket. The word dates from the late 1800s, from bill, or "paper money," and fold, which is thought to be short for folder.