PIRANUS.  A Latinized form of British Piran (q.v.), meaning "little black one." (A Glossary of Cornish Names, Bannister, 1869).

... The first Cornish apostle of any note was Corantinus, born in Brittany, who converted almost all Cornwall, and died A.D. 401.  He was succeeded by a more illustrious man, Piranus, born of noble parents in the county of Ossory, in Ireland, A.D. 352.  He was converted to the Christian faith, visited Rome, was ordained bishop, and sent back to Ireland; he resided in the heart of the island, and his sanctity attracted such multitudes to him, that a town was built near his cell.  At length, wishing to retire from the importunity of crowds who flocked from all parts of Ireland to him, he gave out that he had received a Divine call, and passed over into Cornwall, taking with him his mother and others, who landing at St. Ives, dispersed themselves over the county, and acquired such veneration among the people, on account of their piety, that the Cornish have consecrated almost all their towns to the memory of Irish saints... (Gentleman's Magazine, v.162, 1837)