What is "elwen"

Elwen (also known as Elvan, Elven, etc.) was the name of an early saint or saints venerated in Cornwall and Brittany. The hagiographical material asserts that he came to Cornwall from Ireland in the company of Breage and six others, but this is attested late. A chapel at Porthleven in Sithney parish, Cornwall, dedicated to Elwen, existed from the 13th century until 1549, and in Brittany several sites and placenames are associated with possibly related figures.