Green’s Dictionary of Slang

(Aus.) a vagrant who sleeps in the open air.

1858		Argus (Melbourne) 14 Sept. 5/3: The third [accused] who was described as a regular wharf ‘coiler,’ was fined 40s damages.
1895		Crowe Aus. Sl. Dict. 18: Coiler, a loafer who sleeps in the wharves or gardens.
1945		Baker Aus. Lang.
1973		(ref. to 1890s) ‘Gloss. of Larrikin Terms’ in J. Murray Larrikins 202: coiler: an idler who sleeps on wharves.