Is it ensure, insure, or assure?
c.1200, "allowance, consent, permission," from Anglo-French graunter, from Old French granter, collateral variant of creanter "to promise, guarantee, confirm, authorize," from Latin credentem (nominative credens), present participle of credere "to believe, to trust" (see credo).
early 13c., "to allow, consent, permit," from Old French granter (see grant (n.)). Meaning "admit, acknowledge" is from c.1300; hence to take (something) for granted (1610s). Related: Granted; granting.