Green’s Dictionary of Slang

polly flinder n.

[rhy. sl. both with Cockney pron.; ult. the nursery rhyme, ‘Little Polly Flinders sat among the cinders’]

1. a window.

1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1992		R. Puxley Cockney Rabbit.

2. a cinder.

1992