Green’s Dictionary of Slang

(Aus.) a type of layabout, typified by the wearing of a cabbage-tree hat (a hat made of woven cabbage-tree or cabbage-palm leaves).

1851		Bell’s Life in Sydney 21 June 2/7: Three young gents, of the cabbage-tree mob [...] looked exceedingly glum [...] The trio, company with several other cabbage-tree-ites, amused themslves ][etc.].
1852		G.C. Mundy Our Antipodes I 53: A sort of ‘loafers’ known as the Cabbage-tree mob, a class whom, in the spirit of the ancient tyrant, one might excusably wish had but one nose in order to make it a bloody one!
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpubl. ms.].