Green’s Dictionary of Slang

water mixed with alum or a similar astringent, used to tighten the vaginal muscles by those who wish to counterfeit virginity.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.