Green’s Dictionary of Slang

1. an unpleasant smell, a stink.

1896		E. Pugh Man of Straw 67: Ow, thet Gorgonzola cheese, / Must ha’ bin un’ealthy, I ser-pose! / Fer the ole Tawm cat fell a corp upon the mat / When the nif rose up ’is nose!
1908		A.N. Lyons Arthur’s 10: ‘Gawd!’ says I, ‘for a niff of Limus Reach.’.
1911		Gem 7 Oct. 8: What’s that awful niff?
1946		(con. 1912) B. Marshall George Brown’s Schooldays 19: Now I know where that rotten niff of manure that kept me from sleeping last night came from.
1957		G. Kersh Fowlers End (2001) 180: One niff, and I don’t think I’ll ever eat again as long as I live.
1960		A. Burgess Doctor Is Sick (1972) 147: Don’t think much of the niff in here.
1982		Beano 13 Nov. 8: Cheesy niff!
2003		N. Griffiths Stump 153: — Ew. What’s that niff? Have yeh farted?

2. (UK drugs) cocaine.

2018-20

T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Niff - cocaine.