"iron hook," c.1300, gaffe, from Old French gaffe "boat hook" (see gaffe). Specifically of the hook on a fishing spear from 1650s.
"loud, rude talk," 1825, from Scottish dialect, perhaps a survival of Old English gafspræc "blasphemous or ribald speech," or from gaff (n.1), and cf. gaffe.
"cheap music hall or theater; place of amusement for the lowest classes," 1850s, British slang, earlier "a fair" (1753), of unknown origin.
A concealed device or operation that makes it impossible for the customer to win; gimmick: People started looking for a gaff (1893+ Carnival & hawkers)
[fr gaff, ''a hook'']