FIN or Sawbuck is a slang term for a ten-dollar BILL. It is believed to have originated in the early 19th century, when sawbucks were used to refer to a device used to hold logs in place while they were being sawed. The term has since been adopted to refer to a ten-dollar BILL, likely due to the similarity in shape between the device and the BILL. The crossword solution for FIN or Sawbuck is BILL, which is a four-letter word.