Baronius, followed by Bishop Lightfoot of Durham and others, calls attention to an etymological difficulty which exists in attempting to derive Petronilla from Petros, which at first sight seems so obvious. These scholars prefer to connect the name “Petronilla” not with Petros but with “Petronius.” Now, the founder of the Flavian family was T. Flavius Petro. Lightfoot then proceeds to suggest that “Petronilla” was a scion of the Flavian house, and became a convert to Christianity, probably in the days of Antoninus Pius, and was subsequently buried with other Christian members of the great Flavian house in the Domitilla Cemetery. De Rossi, however, and other recent scholars in the lore of the Catacombs, in spite of the presumed etymological difficulty, decline to give up the original “Petrine” tradition, but prefer to assume that Petronilla _was_ a daughter, but only a _spiritual_ daughter, of the great apostle--that is, she was simply an ordinary convert of S. Peter’s. Of these two hypotheses: (_a_) dealing with the first, in the very free and rough way in which the Latin tongue was treated at a comparatively early date in the story of the Empire, when grammar, spelling, and prosody were very frequently more or less disregarded save in highly cultured circles, the etymological difficulty referred to by Lightfoot can scarcely be pressed, for it possesses little weight. (_b_) As regards the second hypothesis--the shrinking, which more modern Roman Catholic theologians apparently feel, from the acknowledgment that S. Peter had a daughter at all, was absolutely unknown in the earlier Christian centuries. To give an example. As late as the close of the eighth century, on an altar of a church in Bourges dedicated to the Blessed Virgin and other saints, there is an inscription attributed to Alcuin the scholar minister of Charlemagne. In this inscription occurs the following line: “Et Petronilla patris præclari filia Petri.” Now, towards the close of the fourth century, Pope Siricius, between A.D. 391 and A.D. 395, constructed the important basilica lately discovered in the Domitilla Cemetery on the Via Ardeatina; but although the basilica in question contained the historic tombs of the famous martyrs SS. Nereus and Achilles, confessors of the first century, as well as the body of S. Petronilla, he dedicated the basilica in question in her honour. Pope Siricius would surely have never named this important and very early church after a comparatively unknown member of the Flavian house; still less would he have called it by the name of a simple convert of the great apostle.