Green’s Dictionary of Slang

(Aus.) a drunkard; a general term of abuse.

1965

W. Dick Bunch of Ratbags 218: The rest just trained to get fit and to learn to fight so that we would always win when we fought other hoods and the ‘pissos’, as we called them. They were the grown-up squares that inhabited the hotels – just anybody, actually [...] The first time we wore our black, red and white ‘skunk-jumpers,’ as we called them, up to the pub, all the square pissos and honkos picked on us.