Green’s Dictionary of Slang

(Aus.) a boorish, loutish, unsophisticated, ultra-nationalistic Australian.

1976		Bulletin (Sydney) 21 Aug. 21/3: Get the average Ock to take a holiday in his own country.
1982		Bulletin (Sydney) 6 July 65/1: He had tins of beer zipped into the front of his parka jacket, resting on his fat stomach... ‘That’s the historical ock.’.