Meaning

noun an informer or spy working for the police

noun a lawman concerned with narcotics violations

verb cause annoyance in; disturb, especially by minor irritations

originUncertain. Perhaps from Angloromani nok (“nose”), from Romani nakh, from Sauraseni Prakrit 𑀡𑀓𑁆𑀓 (ṇakka), ultimately a doublet of nose.

Etymology from Wiktionary, CC BY-SA 3.0