A valley or glen, probably in western England, where the boar Twrch Trwyth made a stand against Arthur’s warriors during the epic hunt, and killed Gwarthegydd, Tarawg, Rhun, Ysgonan, Gwydre, Garselid, Glew, and Ysgawyn.
Notes
Cwm, means a low place enclosed with hills in Welsh. The Saxonized form is comb or combe, which can be found in the name of cities, such as: Widecomb, Nettlecomb, Kingcombe.
Source
Culhwch and Olwen | Late 11th century