Green’s Dictionary of Slang

Metho n.

[abbr. + -o sfx (3)]

(Aus./N.Z.) a Methodist; also as adj.

[Aus]Rutherford Rumblings (Tamworth) 17 May 1: Why did the 41st pinch our Metho. Padre? [AND].
[Aus]Baker Popular Dict. Aus. Sl.
P. White Riders in Chariot 208: Arch and me are Methoes, except we don’t go; life is too short.
[Aus]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.
[NZ]McGill Reed Dict. of N.Z. Sl.