Is it ensure, insure, or assure?
mid-14c., "wooden framework used in building, etc., temporary structure for workmen to make walls," a shortening of an Old North French variant of Old French eschafaut "scaffold" (Modern French échafaud), probably altered (by influence of eschace "a prop, support") from chaffaut, from Vulgar Latin *catafalicum (see catafalque). Meaning "platform for a hanging" is from 1550s. Dutch schavot, German Schafott, Danish skafot are from French. As a verb from 1540s.