If something is naff, it looks cheap, old-fashioned, or in poor taste — not cool, and a bit embarrassing. A naff souvenir, a naff jumper, a naff pop song: British people say this when something tries to look nice and misses. It is very British informal talk, from about the 1960s. Americans almost never use it; they would more often say tacky or cheesy. Naff is not a heavy swear word. It is a light, slightly snobbish poke at style. You can also tell someone to naff off, which means go away — a softer cousin of a ruder British phrase. Scholars are not sure where the adjective came from. It may have started in Polari, a private-ish slang used by some gay men and show people in Britain, and it may be a cleaned-up twist on ruder words. Treat that origin as “perhaps,” not as a settled story. There is also a South German family name Näff, which only looks similar; it is not this word.