Petronilla

also Petronella, fem. proper name, a Medieval Latin feminine diminutive of Latin Petronius (which is of uncertain origin). Also "the name of a saint much-invoked against fevers and regarded as a daughter of St. Peter. The name was accordingly regarded to be a derivative of Peter and became one of the most popular of girls' names, the vernacular Parnell being still used as a proper name as late as the 18th century in Cornwall" [Reaney]. The shorter form is via Old French Peronelle. By late 14c. it also had become a type-name for "a common woman, a prostitute, a priest's concubine."