Green’s Dictionary of Slang

billjim n.

also biljim, Bill Jim
[the proper names Bill + Jim; the typical Aus. soldier in WWI; a synthetic var., billzac (SE bill + ANZAC) was created by the Aus. press during WWI, but never spread beyond their own columns]

(Aus.) the typical Australian male; used in WWI for an Aus. soldier, thus Bill, Jim and Harry, typical/average Aus. males.

[Aus]Bulletin (Sydney) 12 Mar. 14/3: Billjim saddled his favourite cuddy [...] and struck the Bushman’s rest at dawn next day.
[[Aus]H. Lawson ‘Jimmy Grimshaw’s Wooing’ in Roderick (1972) 450: His mates and the casual Jims and Bills were taken too suddenly to laugh].
[Aus]Bulletin (Sydney) 29 Nov. 11/1: The damsel gives her name as Eileen James, but as nobody knows any James who has lost a small girl, and as no one has claimed her, it seems to be another exposition of the tired feeling that characterises the great tribe of Bill-Jim, alias James.
[Aus]‘Dads Wayback’ in Sun. Times (Sydney) 11 Oct. 6/3: Ther eddicated poet is never read by Bill, Jim, an’ Harry.
H. Lawson ‘The Stranger’s Friend’ in Lone Hand Nov. 17/2: A certain man from Anywhere, call him Biljim, [...] leaves a sick mate at the Half-Way Pub.
[Aus]H. Lawson ‘A Few Remarks on Bill and Jim’ in Roderick (1972) 717: In the first place, there isn’t, and never was, any ‘Biljim’. He’s a monster that was invented by some alleged writer who never knew either Bill or Jim, and is equally unknown to them.
[[Aus]C.J. Dennis ‘The Push’ in Moods of Ginger Mick 40: An’ there’s Bills an’ Jims an’ Bennos, an’ there’s Roys an’ ’Arolds too, / An’ they’re cobbers, an’ they’re brothers, an’ Australians thro’ an thro’].
[NZ]Feilding Star (N.Z.) 3 Mar. 2/5: A long, hungry, Billjim wandered into the new Australian Y.M.C.A. hut.
[Aus]Kia Ora Coo-ee 15 Apr. 4/3: [O]ne of the Billjims, who had a forty horse-power whisky thirst, was sent back to the L.H. dump at Rafa for a spell.
[[Aus]Aussie 12 Mar. 11/1: [caption] Two cobbers, Bill and Jim, in normal condition].
[Aus]Bulletin (Sydney) 19 Feb. 16/3: McDougall, returned Billjim [...] held a temporary job in Melbourne as a grievance-redresser for fellows-Diggers.
[UK](con. WWI) Fraser & Gibbons Soldier and Sailor Words 22: Bill Jim: An Australian. (Australian slang).
[UK](con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier.