Green’s Dictionary of Slang

(Aus. tramp) an old, worn or thin blanket or rag, used as a substitute blanket, carried in a swag.

1897		‘6x8’ [Dick Holt] in Bulletin (Sydney) 7 Aug. red page/4: Blankets - ‘Early risers,’ Old and common. Bush men are seldom burdened with much ‘nap’ (another term for blanket), and on cold winter mornings are hunted out of bunk at daybreak in search of the nearest fire.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.].