watchman (n.)youdaoicibaDictYouDict[watchman 词源字典]
also watch-man, c. 1400, "guard, sentinel, lookout" (late 12c. as a surname), figuratively "guardian, protector" (mid-15c.), from watch (n.) + man (n.). Also "person characterized by wakefulness" (mid-15c.).[watchman etymology, watchman origin, 英语词源]