What's the origin of the word "buck"?
What's the origin of the word "buck," meaning a dollar?
Lots of speculation, no firm conclusions. Next time we start a language we have to keep better notes. The leading theory at the moment is that buck comes from an old practice in poker. Evidently in the 19th century frontier card players were so thick they couldn't remember whose turn it was to deal from one hand to the next. So they placed a counter or token in front of the dealer du jour. This token was called a buck, since it was commonly a buck knife, whose handle was made of buck horn. When the time came for the dealer to surrender the job to someone new, he (you saw this coming) "passed the buck" to the new guy. Uh-huh.
A more plausible theory is that buck is short for buckskin, a common medium of exchange in trading with the Indians. As early as 1748 we have people writing, "Every cask of Whiskey shall be sold to you [Indians] for 5 Bucks." The transition to dollars seems only natural.
Curiously, "sawbuck," a ten-dollar bill, appears to be only indirectly related to buck. It got its name because some old ten-spots were denominated with Roman numeral Xs. The Xs looked like the X-shaped arms of the benches sawyers used to hold up logs for cutting. (Pictogrammic depiction: X-X.) The benches, which were vaguely similar to today's sawhorses, were called sawbucks.