Green’s Dictionary of Slang

dripping, rendered fat, occas. bread and dripping.

1971		J. Jones Rhy. Cockney Sl.
1978		Maledicta II:1+2 (Summer/Winter) 119: Errol Flynn = ‘chin’, Vera Lynn = ‘gin’, and murderer Dr. Crippen = ‘dripping’, as in cookery rather than in the clap, have stayed in the language though they have passed out of the news.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.