Green’s Dictionary of Slang

fried potato n.

also baked potato
[rhy. sl.; note Cockney pron. ‘pertater’]

(US) a waiter.

[US]T.A. Dorgan in Zwilling TAD Lex. (1993) 38: Fried potato – that’s a waiter.
[US]A.J. Pollock Und. Speaks.
[UK]S.T. Kendall Up the Frog 12: I’ve asked the baked potato for a Joe Blake and some rosebuds.