Green’s Dictionary of Slang

(Aus.) a close friend.

1901		Walcha Witness (NSW) 6 July 2/4: our first troop was in front, I and my three cobbos (comrades) were what they call connecting file, about 300 yards behind the scouts [...] my cobbos make me laugh, they draw and cook the poultry, leaving the blood on their hands for days.
1911		Tamworth Dly Obs. (NSW) 6 Oct. 3/2: McCoy is a pal of Frank O’Grady, and is out to avenge his ‘cobbo’s’ defeat.
1916		Maitland Wkly (NSW) 17 June 8/4: Marvellously close come some bullets, and my cobbo and I, after our first two hours of post [...] thanked our stars that we didn’t have stiff necks.
1922		Western Australian (Perth) 28 Oct. 8/8: Since we have been here my ‘cobbo’ and I have been clearing, grubbing timber . . . a pretty mixture.
1933		Dungog Chron. (NSW) 2 May 3/6: Mr. J. T. Pearson also made his annual visit and states that all his old ‘Cobbo’s’ are still on deck.
1946		Muswellbrook Chron. (NSW) 24 Dec. 1/3: During the evening drinks and refreshments were served by a bevy of ‘Diggers,’ and their frist [sic] consideration was the care of the ladies. In this department, Barney and his ‘cobbos’ of the 1914-19 and 1939-45 World Wars did a splendid job.
1953		Muswellbrook Chron. (NSW) 1 May 8/2: On his way back he called in at the ‘big smoke’ and has practically all things arranged for Dick Lewis [...] and his ‘tin lid,’ to visit Muswellbrook at an early date. They will receive a great welcome from his ‘cobbos’.