Ecgtheow, I don't know the last name but Beowulf was raised by the Geats clan which fallowed into the Tevet Clan that is a close clan to each other. (There is NO last names for vikings but clans and tribs.
I hope that help a little.
There is no character named Edgetho in the epic poem Beowulf. It is possible that there is a confusion with the name Ecgtheow, who is Beowulf’s father. Ecgtheow is mentioned in Beowulf as a nobleman and warrior.
Beowulf's father
In "Beowulf: A New Telling," Beowulf's father is Ecgtheow.
Beowulf's full name is Beowulf.
It's Higlac. Hrothgar was the king but he is not related fo Beowulf. Beowulf's father's name is Edgtho.
Beowulf owes a family debt to Hrothgar because Hrothgar's father helped settle a feud and make peace with Beowulf's father, Ecgtheow. Beowulf's father was indebted to Hrothgar's father for his assistance, which Beowulf sees as a reason to repay the debt by helping Hrothgar against the monster, Grendel.
* Ecgþeow was Beowulf's father who belonged to the Swedish Wægmunding clan. He joined the Geats after having been banished for killing the Wulfing Heaðolaf, and married a Geatish princess. * The name of Beowulf's mother is not given in the story, but she is the daughter of King Hrethel and sister of King Hygelac.
He is Beowulf's father.
Beowulf does not fight Grendel's mother until after he has defeated Grendel.
Beowulf killed Grendal and later Grendals mother came to revenge his death
The name of the sword is Hrunting. It was given to Beowulf by Unferth (lines 1455-1458).
I dont believe so many vikings didn't have last names.