The story
Unknown, although possibly from the French phrase "petit cru" (small growth) from Anglo-Norman French "petit creu", thus as a nickname for a small/short man. Other interpretations include from the French phrase "pie de grue" (crane's foot), i.e., someone with long legs (cf. pedigree, from Anglo-French "pe de gru", a variant of Old French pied de gru, "foot of a crane"). Attested from the 13th century as an English surname.
Etymology from Wiktionary, CC BY-SA 4.0.