Is it ensure, insure, or assure?
c.1300, from Anglo-French enditer "accuse, indict" (late 13c.), Old French enditer "to dictate or inform," from Late Latin *indictare "to declare, proclaim in writing," from Latin in- "in" (see in- (2)) + dictare "to say, compose in words" (see dictate). Retained its French pronunciation even after the spelling was re-Latinized c.1600. In classical Latin, indictus meant "not said, unsaid." Related: Indictable; indicted; indicting.