Green’s Dictionary of Slang

(Aus./N.Z.) one who stands a round of drinks.

1863		Lyttelton (N.Z.) Times 31 Dec. 4/1: Perhaps some of our readers do not know the extent to which the practice of ‘shouting’, or of inviting to drink at the ‘shouter’s’ expense, is carried even here.
1885		D.B.W. Sladen In Cornwall and Across the Sea 156: (title) The sigh of the shouter .
1893		H. Lawson ‘When the “Army” Prays for Watty’ in Roderick (1967–9) I 231: We guzzle as we guzzled long before the Army came, / And the loafers wait for ‘shouters’ and — they get there just the same.
1910		Sun. Times (Perth) 17 Apr. 3rd sect. 17/3: Sir John Forrest is, when at Parliament House, the most cheerful and generous ‘shouter’ in the refreshment room.
1925		Age (Melbourne) 30 May 16/4: [headline] ‘Shouter’ Refuses To Drink.
1972		Arthur Chipper Aussie Swearers Guide 85: Drag-the-chain Shouter: Slow to stand drinks.
1982		Les Murray Vernacular Republic 20: Beyond all wars / in the noonday lands of wheat / the whistle summons shouters from the bar / refills the train with jokes and window noise.