naffyoudaoicibaDictYouDict[naff 词源字典]
naff: [20] There seem to be two separate words naff in British slang, but the origins of both are mysterious. The first, naff off, appeared in the 1950s. Functionally it is a euphemistic substitute for fuck off, and there could be some connection with eff, another euphemism for fuck (perhaps the n in an eff wandered out of place). Alternatively it could come from naf, an old backslang reversal of fan in the sense ‘female genitals’.

The second, an adjective meaning ‘unstylish, unfashionable, tasteless’, is first recorded in 1969. Its antecedents are even more obscure. Among possible relatives are northern English dialect niffy-naffy ‘stupid’ and naffy, naffin and naffhead ‘idiot’ and Scots nyaff ‘unpleasant person’.
[naff etymology, naff origin, 英语词源]
naff (v.)youdaoicibaDictYouDict
British slang word with varied uses, not all certainly connected; see Partridge, who lists three noun uses: 1. "female pudenda" (c. 1845), which might be back-slang from fan, shortening of fanny (in the British sense); 2. "nothing," in prostitutes' slang from c. 1940; 3. a euphemism for fuck (v.) in oaths, imprecations, expletives (as in naff off), 1959, "making it slightly less obvious than eff" [Partridge]; and an adjective naff "vulgar, common, despicable," said to have been used in 1960s British gay slang for "unlovely" and thence adopted into the slangs of the theater and the armed forces.