Green’s Dictionary of Slang

coffee-house n.

a privy.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1835		G. Kent Modern Flash Dict. 19: Jones’s, Mrs. – the coffee house, privy.
1848		Flash Dict. in Sinks of London Laid Open.
1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.