Servius on Virgil, Aeneid III, 57: means This expression is derived from a Gallic custom. For whenever the people of Massilia were burdened with pestilence, one of the poor would volunteer to be fed for an entire year out of public funds on food of special purity. After this period he would be decked with sacred herbs and sacred robes, and would be led through the whole state while people cursed him, in order that the sufferings of the whole state might fall upon him, and so he would be cast out. This account has been given in Petronius.