big bucks

Big bucks means a large amount of money, and buck has meant a dollar since the American frontier of the 1700s. Back then deerskins, or buckskins, were a standard and widely accepted form of currency, used for trade long before the official U.S. dollar existed. Settlers and traders bartered animal pelts with Native American tribes; a buckskin was durable, universally valued, and effectively served as a single unit of money.

The usage is recorded directly. In a 1748 journal entry, the Pennsylvania Dutch pioneer Conrad Weiser noted that someone was robbed of 300 bucks worth of goods, and that five bucks would buy a cask of whiskey. In 1824, in Sketches of North American Indians, James Buchanan wrote that each buck-skin was one dollar.