The history of this idiom goes back to the American frontier days. During the early 1700s, hunters killed many deer, using their skins for barter. The male deer is called a "buck", and buckskin was prized as a material for making durable outdoor clothing. In a trading camp, a hunter would pass the buckskin that he'd collected to a trader, who would give him money or goods in return. Because of this association, the American dollar came to be called "a buck". In slang, 1 dollar = 1 buck, and 15 dollars = 15 bucks. Although everyone likes money, the idiom "passing the buck" eventually came to mean passing along something unwanted or undesirable! When a person doesn't want to accept blame for something bad, they may instead blame someone else. Passing on the responsibility for unpleasant things became known as "passing the buck".