可汗 is a loanword for 'khan' (also spelled 'qaghan' historically). It was the supreme title for rulers of steppe empires including the Xiongnu, Rouran, Göktürks, and Mongols. It appears in the famous Mulan ballad (
木兰辞):
可汗大点兵 - 'the Khan is mustering a great army.'
