Liffey water, n. — Green’s Dictionary of Slang

Liffey water n.

[rhy. sl.; the orig. ref. was to Guinness, brewed near the River Liffey in Dublin]

porter (the drink).

1952		M.F. Caulfield Black City 77: ‘It’s the Liffey water,’ said Flynn. ‘I’m told the stuff they get across the water isn’t fit for human consumption.’.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1976		P. Theroux Family Arsenal 276: Let’s do it the Irish way, with a jar of Liffey water.
1997		Share Slanguage.