Green’s Dictionary of Slang

1. to work as a bullock driver’s or truck driver’s assistant, or to help in another occupation; thus swamping n.

1897		Bulletin (Sydney) 6 Mar. 28/4: We were swamping back from Lake Darlot rush last winter with Billy Mills’s camels.
1910		Bunbury Herald (WA) 3 May 2/7: On Wednesday last, while engaged in his usual avocation of swamping for a whim driver, at Argyle, a young man named Frederick Maxwell met with his death.
1926		K.S. Prichard Working Bullocks 101: Billy Williams the bullocky, and Ern Collins who was swamping for him, turned their team into the yards on the following Monday.
1937		E. Hill Ports of Sunset 96: In they came, across the jagged Leopolds, or up from the desert, ‘swamping’ with a bullocky, staggering behind a pack donkey, or on Shanks’ pony [OED].
1938		W. Smitter F.O.B. Detroit 10: That manipulator job [...] I’ll take it. I’d like this man here to swamp for me.
1949		A.I. Bezzerides Thieves’ Market 232: He saw Nick run to his truck. The swamper waddled after him. ‘You’re going to let me swamp for you huh?’.
1951		E. Hill Territory 446: Swamping: Originally travelling with a bullock-team to carry the swag, now joining up with a mailman or any regular traveller.
1958		E. Gilbert Vice Trap 50: He’d got Graemie [...] helping swamp damaged booths and fixtures [...] onto the truck.

2. (Aus.) to travel, to travel with.

1904		Sun. Times (Perth) 25 Dec. 4/7: They [i.e. gold prospectors] swamped it out to Darlot’s Lake.
1906		Sun. Times (Perth) 4 Feb. 1/1: A once blown-out Perth sport has recently swamped back from the East.
1954		T. Ronan Vision Splendid 92: This isn’t my camp, I’m only swamping a ride.
1964		T. Ronan Packhorse and Pearling Boat 170: If I broke it for a tenner, I’d roll my swag and swamp my way back to Queensland.
1984		J. Carson in Ammon Working Lives 155: He promised that if I gave him a hand to load the big wagon I could swamp up with him for as far as I wanted to go.