Green’s Dictionary of Slang

wallop n.²

1. (orig. Aus.) beer, alcohol in general.

1894		Truth (Sydney) 11 Feb. 4/6: Our War Department could supply each yeoman with at least a ‘salt-horse’ sandwich and a pint of ‘wallop’.
1898		Bulletin (Sydney) 29 Oct. 3/3: A glass of beer is a ‘pot of wallop’, and the previous night he was ‘on his pink’, ‘juiced’, ‘wined’, or ‘shikkered.’.
1903		Sun. Times (Perth) 8 Mar. 1/1: The corpulent erstwhile wallop-vendor.
1906		Gadfly (Adelaide) 18 July 18/2: For the last month the bungs have been retailing all the hog-wash in the cellars. Some of them had to close at 9 o’clock, as the supply of wallop had petered out, such was the demand for a final skinful.
1915		Sun. Times (Perth) 11 Apr. 3/2: Dip your beak / In flat colonial wallop.
1927		Sun. Times (Perth) 28 Aug. 6/7: A hogshead of beer that had gone flat and stale [...] was undrinkable by white men and as it was a crime to allow an aborgiinal to get to it, the not wanted wallop had to be got rid of.
1928		Dover Exp. 28 Sept. 9/2: Mr [Ernest] Bevin: ‘I sit down with employers every day of my life.’ Mr. Lewis: ‘They give you a cigar and a pint of “wallop”’ .
1936		J. Curtis Gilt Kid 32: There was no mistake about it the nick had taken it out of him. He could not stand his wallop as well as he had been able to before he had been arrested.
1943		‘Henry Green’ Caught (2001) 45: They drank wallop, that is draught ale.
1957		G. Kersh Fowlers End (2001) 246: ‘Better order wine,’ said he, putting down his empty glass with a grimace. ‘Beer,’ I said. ‘What, can you order wallop from that bloke wiv the silver chain round ’is neck?’.
1960		C. MacInnes Mr Love and Justice (1964) 57: Holding wallop-stained glasses.
1978		F. Norman Dead Butler Caper 143: Shoot down the bar and get the sergeant a pinta wallop.
1981		P. Wright Cockney Dialect and Sl. 93: A drinker might ask instead for a pint o’ wallop.
2000		Guardian Rev. 29 Apr. 12: A pint of the local wallop, please.

2. a measure or swig of alcohol.

1931		Ade Old-Time Saloon 26: The half-naked puddlers coming in to gulp down enormous hookers of straight rye, each heroic wallop being followed by a tall glass of beer as a ‘chaser.’.
2012		T. Pluck ‘Summer of Blind Joe Death’ in Life During Wartime (2018) 160: Mr Collins laughed and slugged back a wallop of shine.

In derivatives

walloper (n.)

(Aus.) a drinker (of beer).

1910		Sun. Times (Perth) 10 Apr. 2nd sect. 9/1: They Say [...] That two of the best beer-wallopers of the institution have forsaken the district [and] the remainder have either fastened on the water-waggon or cut the publican.
1921		Sun. Times (Perth) 16 Oct. 3/3: [headline] Eightpence Per Pot — A Wail of a Walloper.

In compounds

wallop-merchant (n.) [merchant n.]

(Aus.) a publican.

1905

Sun. Times (Perth) 15 Jan. 1/1: Local cuists have dropped billiard-playing with a Claremont wallop-merchant.

wallop shop (n.)

(Aus.) a publican.

1901

W.A. Sun. Times (Perth) 8 Dec. 1/1: The Fremantle p.c. constable has installed his pretty protege in a well-known saloon bar [...] The herring-gutted gendarme is now Protector-in-ordinary to the aforesaid wallop shop.