Green’s Dictionary of Slang

1. a pickpocket.

1902		H. Baumann Londinismen (2nd edn).
1937		B. Dai Opium Addiction in Chicago 202: P.P. Pickpocket.

2. a beggar who encases his legs in plaster of Paris soaked bandages to counterfeit a serious illness.

1903

N.-Y. Trib. 10 May B1: [...] those with legs bound in stiff plaster of paris bandages, who are called ‘P. P.’ men, for their bandages.

3. (Irish) a parish priest.

1922		Joyce Ulysses 598: Because if they didn’t believe they’d go straight to heaven when they die they’d try to live better – at least, so I think. That’s the juggle on which the p. p.’s raise the wind on false pretences.
1965		L. Dunne Goodbye to The Hill (1966) 58: If there was one man in Rathmines that I couldn’t have cared less about it was the P.P., or, as he was known to the kids, Little Jesus himself.