sawbuck (n.)youdaoicibaDictYouDict[sawbuck 词源字典]
"ten-dollar bill," American English slang, 1850, from resemblance of X (Roman numeral 10) to the ends of a sawhorse. Sawbuck in the sense of "sawhorse" is attested only from 1862 but presumably is older (see saw (n.1)).[sawbuck etymology, sawbuck origin, 英语词源]