Green’s Dictionary of Slang

an act of urination; and as a request to use the lavatory (cf. gerry riddle n.).

1934		J. Franklyn This Gutter Life 212: Four’r us – all been on the booze – dunno where – come out for a jimmy-riddle, and I losht ’em!
a.1945		L. Payne private coll. n.p.: Piddle Jimmy Riddle.
1959		R. Fuller Ruined Boys 10: Come and have a Jimmy Riddle .
1969		S.T. Kendall Up the Frog 12: Shan’t be a cock linnet – just going for a Jimmy Riddle.
1975		‘P.B. Yuill’ Hazell and the Three-card Trick (1977) 94: I was also needing a Jimmy Riddle.
1980		Barltrop & Wolveridge Muvver Tongue 11: The rhyming expressions which do get used regularly. ‘Can I have one of your Jimmy Riddles?’ (May I use your toilet?’).
1981		A. Payne ‘You Need Hands’ in Minder [TV script] 47: I’m dying for a jimmy but I daren’t go in case they move on. [Ibid.] 57: Arthur stops, prepares to have a J.R.
1992		I. Rankin Strip Jack 195: Gone for the proverbial jimmy.
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: Jimmy Riddle rhyming slang Vicar friendly term for a piddle.
2001		K. Waterhouse Soho 170: He had a pressing desire for a jimmy riddle.
2007		NY Times 8 Nov. 🌐 If you have to piddle, you say ‘Jimmy Riddle’.