Green’s Dictionary of Slang

1. a bedpan.

1890–1904

Farmer & Henley Sl. and Its Analogues.

2. (orig. Aus.) a shoulder or leg of mutton.

1895		Western Champion (Barcaldine, Qld) 30 Apr. 9/3: A bit of grilled ‘banjo‘ (shoulder of mutton) is not too bad after a 30-mile ride.
1904		Brisbane Courier 30 Jan. 12/7: Old ‘Captain Mulga’ is one of the most amusing of eccentric squatters this writer has had the pleasure of thanking for a ‘banjo’ of mutton.
1910		Northern Miner (Qld) 18 Feb. 7/2: A bit of flour and tea and sugar, or a banjo of mutton to help us along.
1926		Townsville Daily Bull. (Qld) 9 Dec. 7/2: Today a ‘banjo’ of mutton costs as much as we paid for a whole sheep in those days.
1937		Western Mail (Perth) 6 May 10/4: ‘Cock’ rushed up with a banjo of mutton .
1941		Wodonga & Towong Sentinel (Vic.) 7 Feb. 4/4: A good dog at work [...] is a delight, so let us pay for it with a pat on the head for ‘Bluey’ or ‘Scotty’ and a ‘banjo’ of mutton.
1945		Baker Aus. Lang. 80: Banjo, a shoulder of mutton.
1950		Townsville Daily Bull. (Qld) 12 June 7/1: Station owners look twice at [...] a ‘banjo’ (forequarter) of mutton before they allow it to vanish in Billjim’s capacious tuckerbags.
2003		McGill Reed Dict. of N.Z. Sl. 16: banjo Leg of mutton, the shape is reminiscent of the musical instrument.

3. (orig. Aus., also army banjo) a shovel; thus banjo and anchor, a shovel and pick; banjo-swinger, manual labourer.

1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 9: BANJO: bush slang A bush name for a frying-pan: the bush frying pan has a long handle and somewhat resembles a banjo.
1918		Aussie (France) 7 Sept. 4/2: [W]e have a bloke I’d back as a banjo-swinger against any cove in the A.I.F. He’s the daddy of ’em all, and no matter how hot the day is, he never raises a sweat. [...] [H]e shovels so fast he can work in the shade of the muck he shifts.
1925		N.Z. Truth 18 Apr. 1/1: The banjo’s jest as ’ard ter swing / Out ’ere.
1926		N. Klein ‘Hobo Lingo’ in AS I:12 650: Banjo—short handled shovel.
1930		‘Dean Stiff’ Milk and Honey Route 199: Banjo – A short-handled shovel.
1941		‘Soldiers’ Talk’ in Tampa Trib. (FL) 21 July 5/4: army banjo: shovel.
1946		Mezzrow & Wolfe Really the Blues 35: The only kind of music you’ll make around here’ll be with a pick and banjo.
1956		Labor’s Special Lang. n.p.: To coal miners, a banjo is a shovel [W&F].
1962		Ragen & Finston World’s Toughest Prison 790: banjo – A shovel.
1967		Lethbridge (Alberta) Herald 21 Jan. 8/1: Here is a language in which a banjo is a shovel, or perhaps a frying pan.
1991		(con. 1920s) O.D. Brooks Legs 71: I’d rather go there and smell horse farts than tamp ties with a banjo.
1996		P. Temple Bad Debts (2012) [ebook] Came out here with two pounds and holes in his socks. Got a job as a brickie, didn’t know a brick from a banjo.

4. (Aus./US) a frying pan.

1935		Charleston (WV) Daily Mail 27 June 8/8: A ‘banjo’ is a frying pan.
1945		Baker Aus. Lang. 80: Banjo, [...] a frying pan.
1955		N. Pulliam I Travelled a Lonely Land (1957) 230/1: banjo – frying-pan.
1967		see sense 3.

5. a piece of excrement.

1997

Roger’s Profanisaurus in Viz 87 Dec. n.p.: brown sword n. See banjo.