Meaning

noun a simple machine consisting of a wheel with a groove in which a rope can run to change the direction or point of application of a force applied to the rope

originFrom Middle English puly, poley, from Old French poulie, polie (“a pulley, windlass”), from Medieval Latin polidia, plural mistaken for the feminine of neuter polidium, from Ancient Greek πολίδιον (polídion, “little pivot”), diminutive of πόλος (pólos, “pivot, hinge, axis”), from Proto-Indo-European *kʷel- (“to turn”). Associated with pull (verb) by folk etymology.

Etymology from Wiktionary, CC BY-SA 3.0