Why are dollars called bucks?

Answer 1

The word "buck" is short for "buck-skin" (from a deer). Buck-skin's were used as currency once upon a time.

Also, a marker was used in the old west when playing Poker to indicate who had the next deal, it was called the Buck. Later players used a silver dollar to do this, but it kept the name Buck.

Answer 2

The term "buck" as a slang for dollar likely originated from colonial America, where deerskins were commonly used as a form of currency. The skins were referred to as "buckskins," and the term "buck" gradually started being used to denote a dollar due to its association with value and trade.