Is it ensure, insure, or assure?
Old English clif "rock, promontory, steep slope," from Proto-Germanic *kliban (cf. Old Saxon clif, Old Norse klif, Middle Dutch klippe, Dutch klip, Old High German klep, German Klippe "cliff, promontory, steep rock").
Clift has been a variant spelling since 15c. and was common in early Modern English, influenced by or merged with clift, a variant of cleft (n.). Cliff-dweller first attested 1889, American English.
steep slope of earth materials, usually a rock face, that is nearly vertical and may be overhanging. Structural cliffs may form as the result of fault displacement or the resistance of a cap rock to uniform downcutting. Erosional cliffs form along shorelines or valley walls where the most extensive erosion takes place at the base of the slope. Because of their greater gradient, cliffs are subjected to greater erosive action and tend to retreat more rapidly than other slopes.