Is it ensure, insure, or assure?
late 13c., from Old French polie, pulie "pulley, windlass" (12c.) and directly from Medieval Latin poliva, puliva, probably from Medieval Greek *polidia, plural of *polidion "little pivot," diminutive of Greek polos "pivot, axis" (see pole (n.2)). As a verb from 1590s.
A machine consisting of a wheel over which a pulled rope or chain runs to change the direction of the pull used for lifting a load. Combinations of two or more pulleys working together reduce the force needed to lift a load. See also block and tackle.