Green’s Dictionary of Slang

alcoholic refreshment.

1856		G.H. Derby Phoenixiana 162: Being of a naturally arid disposition, and perhaps requiring irrrigation at that particular moment, you unguardedly invite Brown, and your new friend Jones of course, to step over to Parry and Battens, and imbibe [DA].
1890		Dead Bird (Sydney) 17 May 1/2: But mark the merry actor who doesn’t really; drink, / But advocates a little irrigation.
1893		W.K. Post Harvard Stories 246: The first rule was to assist each other in obtaining nourishment and irrigation at the crowded ‘spreads’.