Green’s Dictionary of Slang

1. to gossip, esp. maliciously, to feed another with unpleasant rumours.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 73: One who is addressed in whispers is ear-wigged by the speaker, who is invariably [...] scandalising someone, falsely.
1832		Egan Bk of Sports 300: Sam has satisfied the Sporting World as to his superior qualities [...] in spite of all the assassin-like attempts of persons ear-wigging in the dark.
1896		A. Morrison Child of the Jago (1982) 144: Perhaps an enemy had earwigged Grinder, and told him a tale that had brought about Dicky’s dismissal.

2. to address surreptitiously.

1830

Egan Finish to the Adventures of Tom and Jerry (1889) 247: Previous to which the Oxonian had ear-wigged Kathleen [...] he told her that if she seconded him in having a lark with the fat Knight, she would be well paid for her trouble.

3. to lecture, to sermonize.

1838		Dickens Oliver Twist (1966) 419: Not grabbed, trapped, tried, earwigged by the parson and brought to it on bread and water.
1842		Marryat Percival Keene 167: And by way of a hint, make him your friend if you can, for he earwigs the captain in fine style.
1853		T. Haliburton Sam Slick’s Wise Saws II 142: He turns to his next neighbour, and earwigs him by the hour.
1860		Reynolds’s Newspaper 29 July 8/4: The Maruis of Greca [...] is now in England, probably trying to earwig Lord John Russell into assisting the King of Naples out of his difficulties.
1868		Chester Chron. 18 Apr. 8/2: Ear-Wigging Royalty [...] the gallant Protestant champions are [...] buzzing about the antechambers off the palace, and trying to make capital by back-stair influence.
1875		Liverpool Mercury 26 June 1/2: You have committed a most heinous offence. It is that of trying to ear-wig a judge.
1879		J. Payn ‘The Confiscated Weeds’ in High Spirits I 71: Carker was in the habit [...] of earwigging him.
1885		Freeman’s Jrnl 16 Feb. 6/4: They people went right — going to the illustrious head of the Church, and trying to earwig him against one of the most illustrious men Ireland had ever seen.
1892		Wrexham Advertiser 30 Jan. 6/4: He thought it insulting to the Board to charge them with trying to ‘earwig’ the magistrates.

4. (also ear-wag) to eavesdrop.

1865		Leaves from Diary of Celebrated Burglar 10/1: Everything being shut up outside, there was little chance of being observed ‘ear-wigging’.
1900		Bulletin (Sydney) 15 Sept. 11/1: Not a bit more extraordinary than was to be expected from the way the whole business, as far as the officers were concerned, was earwigged and backstaired to give noodles the chance of a little sham distinction.
1925		Smith’s Wkly (Sydney) 11 Apr. 13/7: While, they were ‘big dooking’ the client in one room He would be earwigging in the next.
1933		C. Drew ‘Gorilla Grogan’ in Bulletin (Sydney) 26 July 40/3: Snatcher shoots a glance around to see if anyone is earwigging.
1951		A. Buckeridge Jennings Follows a Clue (1967) 76: I suppose you’ve been ear-wagging again.
1951		E. Hill Territory 423: When he gets too tired of ‘ear-wiggin’ to a lot o’ ballyhoo, he just uprises and walks away.
1953		I. Hamilton Till Human Voices Wake Us 22: Some screw had been earwigging.
1966		P. Boyle At Night All Cats Are Grey 93: By this time all hands were earwigging [...] conversation had dried up.
1975		Bulletin (Sydney) 26 Apr. 45: In the end all the mugs start earwiggin’ and the store jacks fall . . . shit, man, it was the best go you ever saw and we had to stall.
1981		S. McAughtry Belfast 28: There must have been somebody earywigging [sic].
1987		(con. 1920s) L. Redmond Emerald Square 199: Ernie Mountain was well up in the story and like me, had ear-wigged on the Kipper.
1995		P. O’Keeffe Down Cobbled Streets, A Liberties Childhood 113: You were ear-wiggin’ again [...] to things that should be no concern of yours.
2001		(con. late 1940s) V. Foot Sixteen Shillings And Tuppence Ha’penny 35: I ’eard me dad — I woz earwiggin.
2012		D. O’Donnell Locked Ward (2013) 5: I caught him earwigging outside the office door.
2017		A. Parks Bloody January 51: ‘I earwigged on their conversation on your behalf’.