Is it ensure, insure, or assure?
c.1300, "an inquest;" early 14c., "a search for something" (especially of judicial inquiries or hounds seeking game), from Old French queste "search, quest, chase, hunt, pursuit; inquest, inquiry" (12c., Modern French quête), properly "the act of seeking," and directly from Medieval Latin questa "search, inquiry," alteration of Latin quaesitus (fem. quaesita) "sought-out, select," past participle of quaerere "seek, gain, ask" (see query (n.)). Romance sense of "adventure undertaken by a knight" (especially the search for the Grail) is attested from late 14c. Johnson's dictionary has questmonger "Starter of lawsuits or prosecutions."
mid-14c., "to seek game, hunt," from quest (n.) and from Old French quester "to search, hunt," from queste (n.). Related: Quested; questing.