Is it ensure, insure, or assure?
"blunder," 1909, perhaps from French gaffe "clumsy remark," originally "boat hook," from Middle French gaffe (15c.), from Old Provençal gaf, probably from a Germanic source, from Proto-Germanic *gafa. Sense connection is obscure; the gaff was used to land big fish. Or it may derive from British slang gaff "to cheat, trick" (1893); or gaff "criticism" (1896), from Scottish dialect sense of "loud, rude talk" (see gaff (n.2)).