Green’s Dictionary of Slang

1. a malicious gossip or flatterer.

1789		G. Parker Life’s Painter 177: And the court, mercy on us! There are no words equal to the just painting of its ear-wigs, its sycophants, pensioners, placemen, scouters, masters of the ceremonies, etc.
1822		(con. early 17C) W. Scott Fortunes of Nigel II 41: A pack of mouthers, flatterers, and ear-wigs.
1864, 1867, 1870		Hotten Sl. Dict.

2. a clergyman.

1857		‘Ducange Anglicus’ Vulgar Tongue.
1864, 1867, 1870		Hotten Sl. Dict.
1929		Advertiser (Adelaide) 25 Oct. 32/8: The ‘gloak’ (beggar) who is ‘quisby’ (broke) and cannot find a ‘downy earwig’ (sympathetic clergyman) is enlightened by cryptic signs of the whereabouts of the nearest ‘dolly shop’ (illegal pawnbroker).
1935		A.J. Pollock Und. Speaks 35/2: Earwig, a clergyman.

3. a close, intimate friend.

1835		G. Kent Modern Flash Dict. n.p.: Earwig, a crony, a close friend.
1848		Flash Dict. in Sinks of London Laid Open.

4. (UK Und.) information.

1865

Leaves from Diary of Celebrated Burglar 53/2: Brockey, by means of the ‘sugar’ he raised on the sale of the ‘sticks,’ kept himself from starving until he got an ‘earwig’ of her whereabouts.

5. an inquisitive person.

1907		Sun. Times (Perth) 15 Dec. 4/7: It isn’t enough that i must be pestered with ear-wigs tracking down Sylvester and Mrs Pearson [etc.].
1984		Partridge DSUE (8th edn) 358/2: from ca. 1880.

6. (also earl wiggins, ear-wigger, wiggins) an eavesdropper; and thus poss. an informer.

1865		Leaves from Diary of Celebrated Burglar 151/1: We had the room to ourselves, and were without fear of an ‘earwig’.
1934		P. Allingham Cheapjack 189: There are times when earwigs [...] who listen to one’s conversation, can be very dangerous.
1935		A.J. Pollock Und. Speaks 35/1: Earl Wiggins, a warning to keep quiet, that somebody is listening.
1940		D. Maurer Big Con 295: ear-wigger. Anyone who tries to overhear a conversation. Also wiggins.
1965		L. Haylen Big Red 116: Names like Nosey, Snoopy and Earwig were given to the snoopers who hung around the boss—informing.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxiv 4/4: earwig: A stickybeak. A listener in.
1972		A. Chipper Aussie Swearers Guide 65: Earwig. Eavesdropper.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 10: Being a syrup of fig was not his go. [...] He was no earwig.