the.com/trolley car

means A streetcar that runs on rails through city streets, drawing electric power from an overhead line.

from The 'trolley' part comes from the grooved wheel (a 'troller') that rolled along the overhead electric wire to pick up power — the wheel itself may derive from 'troll' in the old sense of rolling or trundling. By the late 1800s 'trolley' had shifted from naming that little wheel to naming the whole streetcar it powered. Decades later, philosopher Philippa Foot borrowed the humble vehicle for a thought experiment about a runaway car and a lever, and the trolley car picked up a second career as the mascot of moral philosophy.