trolley (n.)youdaoicibaDictYouDict[trolley 词源字典]
1823, in Suffolk dialect, "a cart," especially one with wheels flanged for running on a track (1858), probably from troll (v.) in the sense of "to roll." Sense transferred to "device used to transmit electric current to streetcars, consisting of a trolley wheel which makes contact with the overhead wires" (1888), then "streetcar drawing power by a trolley" (1891), which probably is short for trolley-car, attested from 1889.[trolley etymology, trolley origin, 英语词源]