loophole (n.)youdaoicibaDictYouDict[loophole 词源字典]
also loop-hole, mid-15c., from Middle English loupe "opening in a wall" for shooting through or admitting light (c. 1300), perhaps related to Middle Dutch lupen "to watch, peer;" + hole (n.). Figurative sense of "outlet, means of escape" is from 1660s.[loophole etymology, loophole origin, 英语词源]