Green’s Dictionary of Slang

(usu. UK juv.) to urinate.

1962		S. Longstreet Flesh Peddlers (1964) 90: I want to tinkle.
1978		L. Kramer Faggots 55: Some fegalim tinkle on each other.
1979		B. Gutcheon New Girls (1982) 266: Mrs. Bundle insistently herded the girls upstairs to the powder room. ‘Goodness, what a relief. I’ve been dying to tinkle all afternoon.’.
1989		J. Morton Lowspeak.
1998		G. Plimpton Truman Capote 433: I think he was tinkling in his pants.
2001		Guardian G2 30 Apr. 2: In the loo, there is a sign: ‘Important notice: If you sprinkle, while you tinkle, be a sweetie, wipe the seatie.’.
2009		J. Stahl Pain Killers 200: The port-o-pharmacy [...] that Dinah left on the seat when she went to ‘tinkle’.
2011		S. Kelman Pigeon English 6: Piss and slash and tinkle mean all the same (the same as greet the chief).
2013		A. Sim ‘Through the Perilous Night’ in ThugLit Feb. [ebook] ‘I’m just going to tinkle and then I’ll be on my way’.