Green’s Dictionary of Slang

(orig. Aus.) a Presbyterian; also as adj.

1929		Scone Advocate (NSW) 26 July 2/4: Our banner will be sholdered by James BT, the Cannon, and our Presbo. leeder [sic].
1953		Baker Aus. Speaks.
1972		A. Chipper Aussie Swearers Guide 61: The first thing any full-blooded Aussie does when handling an amen snorter is shorten his denomination to size and add an ‘O’. As in Bappo, Congo, Metho, Presbo, Protto, Salvo, etc.
2018		I. Welsh Dead Man’s Trousers [14]: Pompous Presbo shit with his fucking round-the-world plane ticket.