Green’s Dictionary of Slang

water, as drunk rather than sailed on or swum in.

1946		St.V. Troubridge ‘Some Notes on Rhyming Argot’ in AS XXI:1 Feb. 46: mother and daughter. Water. (Origin doubtful, probably English.) This again, if English, is rare. I have never heard anything except ratcatcher’s daughter (from a popular song of the 1850’s), or didn’t ought ter.
1960, 1975		Wentworth & Flexner DAS.