This well known name is of medieval Italian origin, and is one of the many diminutive forms of the Italian surnames developed from the male personal name Peter. The given name is ultimately of Greek origin, from "Petros", itself derived from "petros", rock, stone, and was extremely popular throughout Christian Europe in the Middle Ages. Its popularity was due in large part to the fact that it had been bestowed by Christ as a byname on the apostle Simon bar Jonah, the brother of Andrew. St. Peter is regarded as the founding father of the Christian Church in view of Christ's comment, "Thou art Peter and upon this rock I will build my Church". In Italy the usual form of the given name is Pietro or Petri, and the diminutive forms of the derivative surname include: Pe(t)rillo, Pe(t)relli, Pitrelli, Perrelli and Pe(t)r(i)ello. Recordings of the name from Italian Church Registers include that of the marriage of Antonio Petrillo and Barbara la Fratta at Castelmauro, Campobasso, on December 12th 1739, and the marriage of Filippo Petrillo and Maria Rosa Figliola, on November 25th 1813, at Roseto Valfortore, Foggia. The first recorded spelling of the family name is shown to be that of Antonio Petrillo, which was dated April 28th 1661, witness at the christening of his daughter, Simone, at Castelmauro, Campobasso, Italy, during the reign of Pope Alexander V11, 1655 - 1667. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.