Green’s Dictionary of Slang

(Aus.) a cab; thus robbo man, a cab-driver.

1900		Bulletin (Sydney) 29 Sept. 22/1: As the regulations re carriage-traffic on the wharf are stringent, the officials did not allow the vice-regal robbo to pass, and the visitor – haw! – had to walk from his steamer to the wharf-entrance.
1900		Bulletin (Sydney) 13 Oct. 28/1: [The new road] is really for the benefit of the four-bob Robbo man who blasphemes to Coogee Bay and through Centennial Park.
1905		Sun. Times (Perth) 1 Oct. 9/3: He darts at the robbo very swift / Bill Burke leaps out and gives him a lift.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 121: ROBBO [...] Robbo [...] let out buggies and hansom cabs at four shillings a day all of which came to be known as ‘four-bob-robbos’ and then by abbreviation to ‘robbos.’ [...] The term spread, and any horse and trap was called by street boys a robbo. [...] Any hired turnout in Sydney slang is a robbo.