Green’s Dictionary of Slang

(Aus.) a generic term of address to a man.

1911		B. Fisher Mutt & Jeff 30 Dec. [synd. cartoon] Ain’t he [i.e. a rabbit] cute? Sit up Steve!
1919		W.H. Downing Digger Dialects 47: steve — Common designation for a casual acquaintance.
1924		(con. WWI) A.G. Pretty Gloss. Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: steve. A casual acquaintance.