 As the name suggests, the lake nestles in a short valley, a cwm, high above the Pen-y-Gwryd hotel.The lake is the source of the Nantygwryd (originally Y Mymbyr), river which in Welsh translates to Pen-y-Gwryd.Prior to 1198 the name Gwryd did not exist in the Mymbyr Valley or Dyffryn Mymbyr.