Green’s Dictionary of Slang

1. ‘one that maintains a Mistress and parts with his money very generously to her’ (B.E.).

c.1698		B.E. Dict. Canting Crew.
1709		N. Ward Compleat and Humorous Account of Remarkable Clubs (1756) 86: And on the luscious Tails of wanton Jades, / Tag Settlements before their Beauty fades: And lest the Keeping-Cully’s Mind should change.
1725		New Canting Dict. n.p.: Keeping Cully, one that maintains a Mistress and parts with his money very generously to her.
1749		Secret History of M--P-- 38: An old batchelor [...] made his addresses to me, not in what we call the honourable way, but with a view of gaining me on terms the men call Keeping.
1753		Dict. of Love n.p.: cully Is one who gives much, and receives at most the appearances of love in return. Their tribe is very numerous: the chief divisions of them are, The marrying-cully, and the keeping-cully. The first is used as a cloak: the second, like an orange, squeezed of its juice, and thrown away.

2. (also keeping-cit) ‘one who keeps a mistress, as he supposes, for his own use, but really for that of the public’ (Grose, 1785); thus keeping lady, a mistress/prostitute [cit n. (1)].

1693		J. Tutchin Western Martyrology 289: The keeping Cully’s Jealousie and Care, / The slighted Lover’s Maggots and Despair .
1703		Shortest-Way with Whores and Rogues 37: The Keeping Lady is at a yearly Expence for a Man that she would have Constant; but she is scarce so herself; for Keeping Ladies are doubly Impudent.
a.1704		T. Brown Dialogues of the Dead in Works (1760) II 312: Away with them into fools paradise, below the keeping-cullies, as the more unpardonable monsters.
1707		J. Dunton Bumography 7: Keeping-Cits are surely Blind, That Doat on Women of their Kind; For Tails are Fireships behind. [Ibid.] 17: The Keeping-Ladys here I mean, Whose Goatish Tails are so unclean.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.