Green’s Dictionary of Slang

a prostitute; a mistress.

1595		Shakespeare Romeo and Juliet I iii: What, lamb! what, lady-bird! God forbid!
1601		Jonson Cynthia’s Revels II i: Is that your new ruff, sweet ladybird?
c.1640		R. Brome Court Beggar I i: A very Limebush to catch Lady-birds?
1648		‘Mercurius Melancholicus’ [title] The Cuckoo's-nest atWestminster, or the parlement between the two lady-birds, Quean Fairfax, and Lady Cromwell, concerning Negotiations of estate, and their severall Interests in the Kingdom; sadly bemoaning the Fate of their Deer and ab-hor’ed husbands.
1699		N. Ward London Spy VII 174: The fright’ned Lady Birds Squeak’d out open’d the Coach Doors, and leap’d out amongst the throng.
1725		New Canting Dict. n.p.: Lady-birds Light or Lewd Women.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
1753		Thief-Catcher 10: When any of these Lady Birds are carried before a Justice, the visible Bully is presently sent for, to vouch their Character, swear any Thing, and bail them.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1821		Egan Life in London (1869) 190: The scheming Procuress, sporting some new-caught lady-birds in a splendid carriage.
1830		Egan Finish to the Adventures of Tom and Jerry (1889) 189: I have lost my ticker; and all my toggery has been boned, I am nearly as naked as when I was born – and the cause – the lady-bird – has hopped the twig.
1844		New Sprees of London 36: We have visited many of the cribs, and found some of them pretty clean, and the lady-birds of a passable quality.
1848		Flash Dict. in Sinks of London Laid Open 113: Lady-bird, a sweetheart, bed-fellow.
1848		‘Ned Buntline’ Mysteries & Miseries of NY 10: ‘I’ll have to see you home, my little lady-bird — by Jove, but you’re a Venus’.
1859		Matsell Vocabulum 49: lady bird A kept mistress.
c.1880		‘US Army Sl. 1870s–1880s’ [compiled by R. Bunting, San Diego CA, 2001] Ladybird A prostitute.
1895		C. Crowe Aus. Sl. Dict. : Ladybird, a kept mistress.
1949		Monteleone Criminal Sl. (rev. edn) 140: lady bird A kept woman; a mistress.