1810, from Scottish Gaelic Gaidheal "member of the Gaelic race" (Irish, Scottish, Manx), corresponding to Old Irish Goidhel (compare Latin Gallus under Gallic, also see Galatians). The native name in both Ireland and Scotland; owing to the influence of Scottish writers Gael was used in English at first exclusively of Highland Scots.
"blunder," 1909, perhaps from French gaffe "clumsy remark," originally "boat hook" (15c.), from Old Provençal gafar "to seize," probably from a Germanic source, from Proto-Germanic *gaf-, which is perhaps from PIE root *kap- "to grasp." Sense connection between the hook and the blunder is obscure; the gaff was used to land big fish. Or the Modern English word might derive from British slang verb gaff "to cheat, trick" (1893); or gaff "criticism" (1896), from Scottish dialect sense of "loud, rude talk" (see gaff (n.2)).