So I went and laid down on the grass. While laying there I piped a reeler whom I knew. He had a nark (a policeman's spy) with him. So I went and looked about for my two pals, and told them to look out for F. and his nark.1879 October, J[ohn] W[illiam] Horsley, “Autobiography of a Thief in Thieves’ Language”, in Macmillan’s Magazine, volume XL, number 240, London: Macmillan and Co. […], →OCLC, page 505, column 1:
the bystander. […] She thought you was a copper's nark, sir. / the note taker [with quick interest] Whats a copper's nark? / the bystander [inapt at definition] It's a—well, it's a copper's nark, as you might say. What else would you call it? A sort of informer.1912 (date written), [George] Bernard Shaw, “Pygmalion”, in Androcles and the Lion, Overruled, Pygmalion, London: Constable and Company, published 1916, →OCLC, Act I, pages 109–110:
1 more example
When we got to the Chief of Police's office a crowd of the most dreadful-looking scoundrels, obviously police narks, informers, and spies of every kind, were hanging about outside the door.1938 April, George Orwell [pseudonym; Eric Arthur Blair], chapter XII, in Homage to Catalonia, London: Secker & Warburg, →OCLC:
2
Australia, Slang An unpleasant person, especially one who makes things difficult for others.
Related terms
copper's nark
nark
verb
Etymology Uncertain. Perhaps from Angloromani nok (“nose”), from Romani nakh, from Sauraseni Prakrit 𑀡𑀓𑁆𑀓 (ṇakka), ultimately a doublet of nose.
1
Slang To serve or behave as a spy or informer; to tattle.
“If you nark on me, I’ll rip your arms off,” said Tim to his brother, as he passed him a joint.