Etymology

• Collins suggests a possible 19th century origin from back slang of fan, fanny.
• AHD suggests a possible dialectal origin but goes no further.
• Wiktionary contributors suggest it is derived from the Polari word naph, and popularised and hence changed its spelling due to being used on the BBC radio programme Round the Horne by Julian and Sandy in the 1960s.
• OED has no evidence before 1966 and mentions the Polari theory and others without going so far as to accept any of them without further evidence.
• Cassell's Dictionary of Slang refers to it being confused. Its etymology is confused with Not Available For Fucking in gay speak (not Polari), an unavailable man. However it is unlikely the word held both these meanings at once by the same group of people. See Cassel's Dictionary of Slang entry
• The BBC show Balderdash and Piffle disagrees with Cassell's.
• Encarta merely state the etymology is unknown.
• Merriam-Webster and Etymology Online offer no information.

Adjective

1. Considered to be poor taste.

   That tie is a bit naff, don’t you think?

2. Bad; tasteless.
3. Something that is poorly thought out, doesn’t really work, or is otherwise not very good.

   That’s a really naff example.

4. Heterosexual.