Green’s Dictionary of Slang

1. (also Yarra bender) an idler, a loafer found on the banks of Melbourne’s Yarra River.

1883		Melbourne Punch 13 Dec. 1/1: 1st Yarra Banker. - ‘Why, Bill, wot ever makes you look so well; your cheeks is a reg’lar aglow with health. 2nd ditto. - ‘Oh! didn’t you know I takes a seaside ’oliday onst a year like the swells, to pick up lost flesh (and loose fowls, he might have added).’ .
1885		Bulletin (Sydney) 11 Apr. 12/2: Do you know what they say of our spirited foreign policy in Victoria? Well, simply that Gladesville must be a lonely place since the contingent left. They also affect to regret that our troops did not wait for their own Yarra-Benders. Only some say this, however. The rest say that none of the Yarra Benders are mad enough to go. These be hard words.
1899		Age (Melbourne) 2 Feb. 9/5: Constable Hede stated that at 2.30 p.m. on the previous day he came upon the old fellow as he was ‘making his bed’ in the Treasury Gardens. He had been living there for the lost fortnight, and was a well-known ‘Yarra banker.’.
1922		E. Dyson Missing Link 🌐 Ch. iii: A feature of Nickie’s very humorous and original impersonation of the Yarra-banker was his waggish begging.
1941		Baker Popular Dict. Aus. Sl.

2. (also Yarra-sider) a soap-box orator; thus Yarra banking, soap-box oratory.

1897		Age (Melbourne) 30 June 5/3: [headline] A Yarra-banker ejected. [...] Do you think you are speaking on the Yarra-bank now?
1900		Bulletin (Sydney) 22 Dec. 18/3: Even the humblest Socialistic Domain orator or Yarra-sider, who howls loosely in a husky beer-voice about ‘the banks’ as the source of all evil, isn’t so primitive in his notions of banking as that.
1905		Truth (Perth) 7 Oct. 8/2: A good many well-to-do professional socialists indulge in a bit of Yarra Banking.
1906		Parliamentary Debates (Victoria) 1111794/2: He (Mr. Bennett) was an agitator for the interests of humanity as a whole. Mr. Bromley. — He was a Yarra-banker at one time.
1943		Baker Popular Dict. Aus. Sl. (2nd edn).