Green’s Dictionary of Slang

congo n.¹

tea.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Congo. Will you lap your Congo with me? will you drink tea with me?
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1819		‘One of the Fancy’ Tom Crib’s Memorial to Congress 2: Whether praying, or dressing, or dancing the hays, / Or lapping your congo at Lord C-stl-r-gh’s.
1822		Life and Trial of James Mackcoull 99: Will you step in and lap your congou with me?
1835		G. Kent Modern Flash Dict. 20: Lapping your congou – drinking your tea.
1840		Flash Mirror 20: T. Potts has opened a rummy slush ken at the sign of the Grouts and Coffee-holder, commonly called the Saloopian Hot-Hell, where he sarves [sic] out, out and out Pekoe soup, Congou broth and brown paint.
1845		J.G. Millingen Jack Hornet 240: My friend , the Duchess of Hagges, never tates fluid [...] she doesn’t even lap congo,.
1848		Flash Dict. in Sinks of London Laid Open.
1867		J. Greenwood Unsentimental Journeys 174: For there’s nought can cheer the heart that’s low / Like a steaming cup of the good congou.