Spanish form of Petronilla, from Roman family name Petronius, possibly meaning rock.
Petronila is the Spanish and Catalan form of Petronilla, a Latin diminutive of Petronia, itself the feminine form of the Roman family name Petronius. The etymology most likely connects to the Greek "petros" (rock, stone) — the same root as Peter — though some scholars trace it to an Etruscan origin, reflecting Rome's complex cultural inheritance. The Petronii were an old Roman family, and the name carried the weight of ancient patrician lineage even as it passed into Christian use.
Saint Petronilla was venerated as an early Christian martyr, traditionally identified — without historical basis but with great popular devotion — as the spiritual daughter or actual daughter of Saint Peter. This legend made Petronilla an object of intense Frankish royal veneration; the Carolingian kings claimed her as their patron saint, and a magnificent chapel dedicated to her once stood at Saint Peter's Basilica in Rome. Her feast day, May 31, was observed with great ceremony by the Franks.
The name thus carried royal and apostolic associations across medieval Europe, particularly in France and the Iberian Peninsula. Petronila gained particular historical significance in medieval Catalonia through Petronilla of Aragon (1136–1173), Queen of Aragon whose marriage to Ramon Berenguer IV, Count of Barcelona, united the Crown of Aragon and the County of Barcelona — a political union that shaped the medieval Western Mediterranean. Her reign marks the founding of what became one of the great medieval powers of Europe. Today the name remains in use across Spain and Latin America, holding its ground as a name of considerable antiquity and regal association.