What is "mabyn"

Mabyn, also known as Mabena, Mabon, etc., was a medieval Cornish saint. According to local Cornish tradition she was one of the many children of Brychan, king of Brycheiniog in Wales in the 5th century. The village and civil parish of St Mabyn is named for her, and the local St Mabyn Parish Church is dedicated to her.