handler (n.)youdaoicibaDictYouDict[handler 词源字典]
late 14c., "one who handles" anything, agent noun from handle (v.). Specific sense of "one engaged in trade" is from 1690s; that of "prizefighter's assistant" (1916) was earlier used in reference to dogfights and cockfights (1825).[handler etymology, handler origin, 英语词源]