In British thieves' slang swag was 'a thief's plunder or booty; a quantity of goods unlawfully acquired'. The term appears in Grose's 1811 Dictionary of the Vulgar Tongue, where one of the definitions is 'any quantity of goods'. James Hardy Vaux, who was a convict in Australia, includes the term in the slang dictionary compiled in 1812 and published in his Memoirs in 1819: 'The Swag is a term used in speaking of any booty you have lately obtained'.
In Australia the term swag was transferred from the quantity of goods acquired by a thief to the possessions carried by a traveller in the bush..
The term is defined in The Australian National Dictionary thus: 'The collection of possessions and daily necessaries carried by one travelling, usually on foot, in the bush; especially the blanket-wrapped roll carried, usually on the back or across the shoulders, by an itinerant worker'.
The earliest citation for this meaning occurs in the Sydney Herald 10 November 1841: 'They gave me back my horse, and on him we fastened 'our swags' (for be it known, they scorned to take our dirty linen).
Other citations in the Australian National Dictionary include:
1859 'Eye Witness' Voyage to Australia: The digger's mode of travelling is very distressing, as they generally carry with them all their utensils and tent covering; the weight of these things approaching near one hundred weight [sic].
The term or name given to this load is 'swag', which is made up in the following manner; his blankets are spread out, the shirts and small clothing are laid on them and rolled like a thick rope until it resembles a horse's neck-collar with both ends tied; this is thrown across the shoulders as a sportsman carries his shot-belt; to this is tied a pannikin, an axe to cut wood, a billy to boil and carry water in one hand, and a green bough in the other to ward off the flies from his eyes.
1890 Bulletin: Did you ever take 'the wallaby' along some dreary track
With that hideous malformation, called a swag, upon your back.
1962 V.C. Hall, Dreamtime Justice: 'Where are your teeth, Mr Morck?' There was a placatory note in the old mail-rider's voice as he told her his teeth were in his swag.
The verb swag meaning 'to carry one's swag' appears in the 1850s, and the compound swagman ('a person who carries a swag; an itinerant worker, especially one in search of employment, who carries a swag; a tramp') appears in the 1860s.