This from Vox Hiberionacum, in a post outlining the bad opinion the classical world had of the Irish:
Perhaps the most appropriate example is that of St. Jerome. Writing against an apparently British opponent Pelagius in the early fifth century, he found it most suitable to insult him using scotti subtext; stolidissimus et scotorum pultibus proagravatus, ‘most stupid and heavily weighed down/pregnant with Irish porridge‘ (Jerome CCL 74 Praef. in Jerem., Lib. I and III). Not only was he engaging in the late antiquity equivalent of calling him fat and stupid (‘Yes, Pelagius, your bum DOES look big in that…’) he also found room for a double insult by labelling the bodily excess as tainted with Irish origins/characteristics.
Pelagius had been acclaimed for his piety and learning, but fell foul of Jerome, Augustine and others while opposing the idea of predestination. They understood him as saying that divine aid was not required to perform good works, that human reason was capable of providing implicit knowledge of God and as denying original sin. For Pelagius, sin was a matter of custom and habit rather than an inherent part of fallen human nature. Pelagius was declared a heretic by the Council of Carthage.