Cynchwr
An Arthurian warrior who was the son of Nes.
He is borrowed from an non-Arthurian Irish hero named Conchobar son of Ness/Conchobor mac Nessa, who appears in the Irish Ulster cycle.
See also
Culhwch | The Legend of King Arthur
Dechtire | The Legend of King Arthur
Ulster | The Legend of King Arthur
Source
Culhwch and Olwen | Late 11th century