Green’s Dictionary of Slang

1. a strike-breaker.

1865		Pall Mall Gazette 19 Oct. 9/2: If the timber merchants persist in putting on blacklegs, a serious disturbance will ensue, as the men on strike are determined to hold out until the end is gained .
1876		Dly Gaz. for Middlesborough 16 June 3/1: He is considered a ‘blackleg’. The strike has caused a serious interruption.
1880		Bulletin (Sydney) 29 May 2/4: Four Newcastle women have been fined £2 each for assaulting ‘blacklegs’ put on to supply their husbands’ places daring strike.
1890		Sporting Times 4 Jan. 1: [He] considers it a shame that the police should be allowed to enter the gas works and protect a lot of honest men, whom, simply because they are industrious, he denounces as ‘blacklegs’.
1893		H. Lawson ‘Coming Across’ in Roderick (1972) 185: Then the boss came along with two blacklegs.
1899		A. Binstead Gal’s Gossip 37: Crushed to death by blacklegs against the corner of a tramcar [...] during the first day of the Strike.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 18: BLACKLEG: a man who accepts work where other men are on strike: a non-union man.
1901		H. Lawson ‘Send Round the Hat’ in Roderick (1972) 473: They loved ’em even as union shearers on strike love blacklegs brought up-country to take their places.
1912		Brisbane Courier 28 Aug. 9/4: Witness protested, and defendant said, ‘Why, you’re only a blackleg’. One of the other men said to witness, ‘Scab’.
1922		E. Raymond Tell England (1965) 133: There are to be no dam black-legs.
1930		(con. 1900s–10s) Dos Passos 42nd Parallel in USA (1966) 209: People yelled at them Blacklegs Scabs but those that weren’t wops were muckers.
1938		G.G. Korson Minstrels of the Mine Patch 311: Blackleg: An opprobrious name for a strikebreaker.
1945		(con. 1900s) S. O’Casey Drums Under the Windows 265: No scab or blackleg could be one of them, and every member, whenever possible, had to be member of a trade union.
1978		A. Burgess 1985 (1980) 193: You blackleg bastards up there [...] Get off that filthy job.
1999		A. O’Hagan Our Fathers 84: ‘You’re just like spoilers and Tories the same,’ he shouted. ‘Blacklegs.’.
2024		J. Meades Empty Wigs (t/s) 916: Not forgetting they also get so-called blacklegs and scabsluts who will do him for nothing.

2. in attrib. use of sense 1.

1894

Truth (Sydney) 29 July 1/1: A month’s gaol for calling blackleg shearers ‘scabs’ is pretty rough, but scarcely more than one could expect from a nigger-driving province like Queensland.

3. in ext. form of sense 1, an informer.

2013

K. Sampson Killing Pool 10: That fool [...] think ol’ Shakespeare going to suddenly turn blackleg and sell my kith and kin down the river .