Green’s Dictionary of Slang

niffy-naffy fellow n.

[Yorks. dial. niff-/niffy-naffy, trifling]

a trifler, an unimportant person.

[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.