Green’s Dictionary of Slang

a waiter (cf. hot potato n.² ).

1960		J. Franklyn Dict. of Rhy. Sl. 52/2: Cold Potato Waiter. Current in theatrical world.
1969		S.T. Kendall Up the Frog.
1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.