Green’s Dictionary of Slang

1. diarrhoea.

1952		T.A.G. Hungerford Ridge and the River (1966) 200: You look crook! You still got the Jim-brits?
1955		D. Niland Shiralee 44: Men was growlin’ crook tucker, gettin’ the jimmies, an’ all that.
1959		D. Niland Gold in the Streets (1966) 168: Strike a light, Danno you gimme the jimmy britts at times.
1960		J. Franklyn Dict. of Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1989		J. Morton Lowspeak.
2002		Pete’s Aussie Sl. Home Page 🌐 Jimmy Britts: the shits.

2. fig., nerves, fears; esp., in phr. give (someone) the Jimmy Britts, to unnerve, to irritate.

1957		D. Niland Call Me When the Cross Turns Over (1958) 48: Thirsty weather, this. Give you the jimmy brits.
1969		Westerly (WA) 27: Yeah — it’s like I read in the Reader’s Digest, once, about this bloke, his wife gives him the jim-brits.
1990		S. Kaye Something Rotten 164: Does it frighten you?' 'It gave me the Jimmy Britts when I first saw it.
1999		G. Seal Lingo 137: When one has the jimmy britts [...] one is upset, rhymed after the US boxer Jimmy Britt (1879–1940).
2002		A. Young Light Years 47: Howda, sport, this dump gives me the Jimmy Britts. What's the oil on the nightlife?
2010		R. Kirkwood Variant Breed 142: The ghostly tales put the ‘Jimmy Britts’ up Kaye.