(Outside of my usual writing focus I realize, but I'm something of an amateur history buff so bear with me.)
Patricius was a Romano-Briton who lived at some point during the 5th century (histories of the period are somewhat imprecise). Patricius was a teenager when he was kidnapped and enslaved by Irish pirates, known as Scoti (from which the name "Scotland" is derived). Patricius remained in captivity for six years before escaping and returning to his family in Britain.
Patricius credited God with his escape and henceforth devoted his life to the study and spread of Christianity. When Patricius was much older, Patricius returned to Ireland, this time as a missionary. Although his mission was not entirely successful and he was beaten, robbed, and imprisoned by local kings, Patricius is credited with introducing Christianity to the Irish and is today recognized as Saint Patrick, the patron saint of Ireland.
Many historians now believe that Saint Patrick, like many early medieval saints, is in some part a composite figure. Although there is little doubt that Patricius himself existed and that the basic details of his story most likely occurred, it is possible that some actions attributed to him were actually performed by Palladius, an earlier Gallo-Roman missionary who visited Ireland in the early 5th century, before Patricius' mission. Medieval hagiographers appear to have conflated the two in later tradition, to the point of Palladius becoming nearly forgotten.