Petronilla is an ancient saint's name that relates to the Roman family name Petronius, thought to mean yokel or woodpecker, though some connect it with Petra or Peter, meaning stone. With the resurgence of so many ancient Roman names, the elaborate and pretty Petronilla or its French form Petronille seem more usable these days than they have in centuries.

So many names sound better with a French accent, and Petronille is one of them: it feels unusual in an elegant way. Usually spelled as Pétronille, it is derived from the Latin Petronius, possibly meaning "yokel", which is now considered a slur for country dwellers, but it may previously have referred to the green woodpecker instead, which is a better meaning. Alternatively, it can be linked to Peter, as Saint Petronilla was said to be Saint Peter's daughter.

Old French form of Petronilla borne by Perenelle Flamel (1320-1402), alchemist and wife of Nicolas Flamel. They are known for their quest to discover the philosopher's stone, a legendary substance said to turn any metal into gold and to make its owner immortal. The figure of Perenelle Flamel appeared in the Harry Potter series.