sawbuck

It has been suggested that the word sawbuck came to mean a 10-dollar bill because the X-shaped ends of a sawbuck look like the Roman numeral for 10. This explanation is problematic because earliest known use of sawbuck in print, from 1850, refers to a 10-dollar bill, not a sawhorse. But we won't rule out the possibility that the sawhorse sense was used in speech before 1850 and just didn't appear in print until later. If you are wondering about buck, we can tell you that it first appeared in print as a word for dollar in 1856 - six years after the first recorded use of sawbuck for a 10-dollar bill.