Is it ensure, insure, or assure?
late 14c., "hurt, harm, injury, pain," from Old French ofense "offense, insult, wrong" (13c.) and directly from Latin offensa "an offense, injury, affront, crime," literally "a striking against," noun use of fem. past participle of offendere (see offend). Meaning "action of attacking" and "feeling of being hurt" are both first recorded c.1400. Sense of "breach of the law, transgression" is first recorded late 14c. Sporting sense first recorded 1894.