In crosswordland, the most famous Peter is probably Biddlecombe. The second most famous must be 'safe'.
Peter is slang for 'safe', as in money box. The origin of the word is unclear. Some sources say it comes from the same root as the Biblical St Peter – the Greek word for rock Petra, since safes are supposed to rock solid. Others say it comes from the Cockney rhyming slang Peter Pan = can, where 'can' could mean 'safe' or 'prison cell' - both safes and prison cells are enclosed spaces and need to be hard to break into/out of.
Here is an extended discussion on the derivation of the word.
Whatever the etymology, cryptic crossword setters have taken to the 'safe' meaning of Peter extremely well.
Independent 8025 (Dac): Plate wife kept in safe (6) PEWTER
W (wife) in PETER (safe)
Using the false capitalization trick, 'Peter' can pass off as a proper noun on the clue's surface and transform to SAFE in the wordplay.
Times 24553: Peter gets into position for a bit, being cautious (2,3,4,4) ON THE SAFE SIDE
SAFE (peter) in ON THE SIDE (position for a bit)
Guardian 25657 (Araucaria): Safe merchants with theatrical personality (5,7)
Times 24767: Play safe with hammer (5,3)
FT 13327 (Mudd): A force kept within safe limit (9)
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