Niffie is an old Dutch street-
slang word used to refer to a knife. It appeared mainly in older street culture and youth
slang before modern
slang terms became popular. The word is used in informal situations, often with a playful or slightly cautionary tone.
Etymology:
Derived from the English word knife. In street slang, knife shifted to nife → nif → niffie, with the “-ie” ending adding a typical Dutch informal sound.