Green’s Dictionary of Slang

naf n.2

also naff

1. nothing [coined in prostitute use].

[UK]Partridge DSUE (8th edn) 774: [...] since ca. 1940.

2. (S.Afr.) a fool, a weakling, an ineffectual person.

[SA]cited in J. & W. Branford Dict. S. Afr. Eng. (1991).