The Irish Damnonians were known as the Fir Domnann or the Fir Bolg. They settled in Connacht and Leinster. In the Irish legends they were said to have descended from Semion of the Nemeds. Nemed indicates a British origin. An entry for King Alexander II attests this. In legend, the Nemedians revolted against the Formorians but the Formorians killed all but thirty of the usurpers. The surviving Nemedians leave Ireland and colonise Britain, but the descendants return to Ireland as the Fir Bolg and the People of Dana. The Strathclyde Damnoni would have their own myths and legends.
When the Romans invaded southern Scotland and established the Antonine Wall, the Damnoni were friendly towards the Romans. They seem to have established an alliance with the Romans in the reign of Theodosius becoming one of what the Romans called foederati : a trusted native tribe which defended its (Roman) borders, especially when the empire was in decline.
This foederati of the Damnoni would have led to the establishment of Roman civitates; not in the original sense of Roman citizenship, but rather a self-governing area with its own administration and laws. Theodosius called this area Valentia after Valentian, the Emperor of the time. Out of this grew the establishment of Strathclyde with its local kings, particularly at a time when the Roman influence was waning.
The Roman tradition of a local council, or ordo, was still maintained. This ordo was made up of decuriones.A decurion would have normally been someone with property, owning a country estate with servants and maids. A decurion would have been responsible for the collection of tax in order that local projects like repairing roads, heating public bathhouses and building city walls were carried out. Once appointed a decurion, the laws made it almost impossible to change career, and often this responsibility passed down from father to son. Stephen Johnson in his Later Roman Britain notes: "To assess how onerous or otherwise all these duties were is no easy task. During the course of the fourth century, emperors were continually at pains to make sure that decurions did not shirk their duties, for it was on them that responsibility for the running of much of the system lay. Decurions were forbidden - it was an apparently increasing tendency - from retiring to their country estates and living a life away from the cares of the civitas... In general the inheritance of property was enough to compel the heir to take on the financial and public responsibilities which were legally tied to the property."
In the foederati state that became the basis of Strathclyde, the Damnonii had less allegiance to the emperor of Rome. The region was controlled by Quintilius Clemens, a Roman, originally it is thought from the Mediterranean. Although run as a Roman state, doubtless many of its practices were more flexible. Two of the region's most famous sons took advantage of this flexibility and eschewed the family tradition of becoming decurions to enter the church. Stephen Johnson, from Later Roman Britain, notes "Pelagius, who was sent away to Italy to study law, and whose controversy with St Augustine about the doctrine of grace gave birth to the 'Pelagian' heresy which gained a great following at least in Britain in the early years of the fifth century." The other, probably more correctly described as non-Pelagian than anti-Pelagian, was St. Patrick.
St. Patrick's father, Calpornius was a decurion, living near Old Kilpatrick. John Morris in his Age of Arthur notes that "when Patrick denounced the depravations of the Clydesiders under Clemens' grandson Coroticus [Ceretic] about the 450s, he protested that their behaviour made them
not citizens of the holy Romans, but of the devil, living in the enemy ways of the barbarians.
The Damnonii of the Clyde had never themselves been Roman citizens; to Patrick, the prefect's grandson and his men were still Romans appointed to rule barbarians, but they had succumbed to his subjects way of life."
The fact that St. Patrick and Pelagius both were able, as sons of decurions, not to follow their fathers profession is a strong indication that they came from a foederati. South of Hadrian's Wall was a legitimate part of the Roman Empire, and its rules would have been more rigorously upheld. Pelagius is commonly thought to have been from Strathclyde, probably Alcluith (Dumbarton). St Patrick's provenance is more widely contested, although Kilpatrick in Dunbartonshire has long been favoured. This claim, I will assert in the entry for St. Patrick, is backed by evidence and is entirely valid.
Ptolemy, the Roman geographer, gives names of some of the towns of Damnoni: Colanica, Vindogara, Coria, Alauna, Lindon and Victoria. It is difficult to ascribe modern place names to any of these sites. The first, Colanica, is mentioned by another geographer, Ravenna, as one of ten cities along the length of the Antonine Wall; the full list being Velaunia, Volitanio, Pexa, Begesse, Colanica, Medio Nemeton, Subdobiadon, Litana, Cibra and Credigone. In his Celtic Placenames of Scotland W.J. Watson offers Girvan as Vindogara; Dumbarton (AlCluith) as Alauna; and Balloch as Lindon. Renwick and Watson in their History of Glasgow, Volume 1, Pre-reformation period offers Colanica as being near the source of the Clyde; Coria near Carstairs; and alternatively, Vindogara as being either Paisley or Loudoun Hill.