Hywel m. Old Breton ho, Middle Welsh hy 'pleasing, good' + an uncertain element.
The name of a 5th-6th C Breton saint, a 9th C Welsh king, a 10th C Brittonic king, two 10th C Welsh kings, two 11th C Welsh kings, and a 12th C Welsh prince.
Howel(l) is an English form.