Is it ensure, insure, or assure?
early 15c., "lead the way; occur before," from Middle French preceder and directly from Latin praecedere "to go before," from prae "before" (see pre-) + cedere "to go" (see cede). Meaning "to walk in front of" is late 15c.; that of "to go before in rank or importance" is attested from mid-15c. Related: Preceded; preceding.