Green’s Dictionary of Slang

an arrogant, pretentious woman of any class; also attrib.

1856		Hereford Times 29 Nov. 6/3: Complainant called her ‘Lady Muck,’ and other opprobrious names [...] and turned her out of the house.
1880		Liverpool Mercury 30 Sept. 6/5: he left his wife in a shop [...] he heard her talking loudly [...] and found that a man named Joseph Parker had been calling her ‘Lady Muck’.
1901		Truth (Brisbane) 12 May 7/3: Lady Muck, who he was rumin, / Goes invokin of the law.
1936		(con. 1830s–60s) ‘Miles Franklin’ All That Swagger 111: Fat old thing! Thinks she’s Lady Muck, and we are the dirt beneath her feet.
1950		C. Harris Three-Ha’Pence to the Angel 200: ‘Ted!’ It was Mavis [...] ‘Lady Muck!’.
1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 33: They put on dog and start acting like they was Lady Muck.
1977		A. Bleasdale Who’s Been Sleeping in my Bed 98: Y’think y’the King of the Castle, Lord and Lady Muck, lookin’ down on the rest of us.
1989		M. Amis London Fields 93: Half the time she’s coming on dead tasty. And I mean sorely in need of it. And then, you know, suddenly it’s Lady Muck.
1984		P. Corris ‘Mother’s Boy’ in Heroin Annie [e-book] ’A tall oman, white hair, well turned out’ [...] ‘Real lady muck’.
1999		Indep. 17 Aug. 12: I pulled up in a sleek black Mercedes [...] and entered our shabby building like Lady Muck.
2001		K. Waterhouse Soho 74: She might be a has-been, but she hadn’t lost her Lady Muck ways.
2017		Guardian Guide 17-23 June 11/1: British people having tea and carrying on like Lord and Lady Muck.
2021		L. McInerney Rules of Revelation 240: [S]he’d thought Mother Jones to be a common nickname, like Lady Muck or Missus Mop.