Green’s Dictionary of Slang

1. a cheating gamester.

1680		Crackfart & Tony 6: The Cheats, the Hectors, the Bullies, and the Shirks in the Baudy-houses, Play-houses, Gaming Ordinaries.
c.1698		B.E. Dict. Canting Crew n.p.: Shurk c. a Sharper.
1984		Partridge DSUE (8th edn) 1052/1: shirk [...] ‘shark, sharper’, ‘needy parasite’ [...] Also sherk, shurk .

2. as a general insult.

1691

‘Person of Quality’ The bragadocio 54: Amaz. Thou pitiful, profligate Shirk;—He that gives thee but a Pot o’ Brandy’s thy Darling.

3. a sponger, a parasite.

1893

‘’Arriet on Labour’ Punch 26 Aug. 88/1: But work-girls work, and that is more than Sam and ’is sort — drat ’em! / When I see shirks platforming, Poll, I’m longing to get at ’em.