On the American frontier in the mid-to-late 1700s, deer hides were especially valuable. However, they were also common enough to be used in lieu of currency, as a medium of exchange where one high-quality skin equaled one dollar. It is for this reason- the adoption of buckskins as a bartering tool equivalent to US currency- that we began using the word buck as slang for "dollar". The phrase pass the buck (meaning "to shift responsibility") dates back to the 1860s, when card players would use a marker made out of buckskin to indicate whose turn it was to deal. This prompted Truman to say the buck stops here in 1952, giving us that phrase. Now, the word buck itself comes from the Old English word bucca, which actually referred to male goats, and only got applied to deer later. This, through Proto-Germanic bukkon, comes from the Proto-Indo-European reconstruction bhugo, with the same meaning.
Adam Aleksic, a leading contender for valedictorian of his high school, is a 215-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and probably isn't spying for the Uzbek government.
The Etymology Nerd