Gwenhwyfach

The tradition surrounding her is preserved in fragmentary form in two Welsh Triads and the Mabinogi tale of Culhwch and Olwen.

This relatively obscure figure is first mentioned in Culhwch and Olwen, where her name (spelled Gwenhwyach) is among those 200 men, women, dogs, and horses invoked by the hero Culhwch to punctuate his request that King Arthur help him find his love Olwen.

Triad 53 lists as one of the "Three Harmful Blows of the Island of Britain" the slap that Gwenhwyvach gave her sister that caused the Strife of Camlann.

Identifying Camlann as one of Britain's "Three Futile Battles", Triad 84 mentions it was started because of a dispute between the sisters.

[1] Melville Richards and Bromwich previously suggested that the alternate spelling of her name in medieval Welsh sources, Gwenhwywach, could have been understood as Gwenhwy-fach, or "Gwenhwy the Lesser", a back-formation based on a false etymology of her sister's name as Gwenhwy-fawr, meaning "Gwenhwy the Great".