Bede the Venerable — as excerpted in the Catena Aurea on Mark 5:1-20

“(ubi sup.) Who dwelt in the tombs, because they delighted in dead works, that is, in sins; who were ever raging night and day, because whether in prosperity or in adversity, they were never free from the service of malignant spirits: again, by the foulness of their works, they lay as it were in the tombs, in their lofty pride, they wandered over the mountains, by words of most hardened infidelity, they as it were cut themselves with stones. But he said, My name is Legion, because the Gentile people were enslaved to divers idolatrous forms of worship. Again, that the unclean spirits going out from man enter into swine, which they cast headlong into the sea, implies that now that the people of the Gentiles are freed from the empire of demons, they who have not chosen to believe in Christ, work sacrilegious rites in hidden places.”