Nelson (Riddle), n. — Green’s Dictionary of Slang

Nelson (Riddle) n.

[rhy. sl. = piddle n. (2); ult. US composer/arranger Nelson Riddle (1921–85)]

(Aus.) an act of urination.

1982		J. Sullivan ‘The Long Legs of the Law’ Only Fools and Horses [TV script] I won’t be able to go for a Nelson Riddle without you giving me a blueprint.
2002		Pete’s Aussie Sl. Home Page 🌐 Nelson Riddle, Nelson: a piddle.