Green’s Dictionary of Slang

(Aus.) a fool, simpleton.

1906		E. Dyson Fact’ry ’Ands 93: Pullin’ legs is dead easy, any gazob kin pull er leg.
1914		Bulletin (Sydney) 17 Dec. 44/2: I was wild, I can tell yer. [...] So I goes, chewin’ over bein’ caught by that gazob.
1916		‘Turner O. Lingo’ Aus. Comic Dict 6: Yob - A gasob. He neither gases or sobs, only sonks and mooches.
1926		J. Doone Timely Tips For New Australians 18: GAZOB. — A slang word for a fool.
1927		Capricornian (Rockhampton, Qld) 22 Dec. 6/3: ‘If you had been there, Ted, it would only hare been a big gazoob after a big prize.’.
1935		A.J. Pollock Und. Speaks.
1945		Baker Aus. Lang. 130: Fools of one kind and another have carved a considerable niche for themselves [...] gammy, gazob, gimp and gup.