From Wiktionary, the free dictionary
Uncertain; perhaps compare prat, fanny, prannet.
pranny (plural prannies)
- (UK, slang, dated) The female genitals.
1985, Paul Quarrington, The life of Hope:And stop staring at my daughter, man! She's got nothing but bubs and a pranny like any other gal!
- (UK, slang) A fool; an idiot.