G'day Jerry,'Polly Perkins' is shorthand for Pretty Polly Perkins of Paddington Green and is in the DT under that name. I sort of cheated - I searched for Paddington, but that amounts to prior knowledge. I guess Pretty Polly would get you a bunch of murder ballads as well, but you would also get 'Pretty Polly Perkins of Paddington Green' - if you recognised it by that title.
I have always taken it that Cushy Butterfield was an English (Geordie?) parody of the music hall song 'Polly Perkins'.
Regards, Bob Bolton Bob Bolton