He was the son of Alduin I. According to one source, his surname, or sobriquet, was acquired due "...from the way in which he cut down a Norman Sea-king through his coat of mail."
Ayahandanya adalah Alduin I. Menurut satu sumber, nama keluarganya, atau julukan, diperoleh karena "...dari cara dia memotong raja Laut Norman melalui mantel suratnya."