Aurel comes from ✶awādelo as said
but Oarel comes from ✶atvadelo
WJ page 363: '3(c) Aurel < *aw(a)delo. Oärel < *atvadelo.'
In WJ page 200 t is seen that S. Amon Gwareth was changed to Amon Gwared... They are not variant forms... As I see it the suffic -eth was outdated and Gwared seems rather like an adjective giving it the meaning of Guarded Hill...