The Laxdaela Saga, tr. by Muriel Press, , at sacred-texts.com
After that Ketill made a great feast, and at it he married his daughter Thorunn the Horned to Helgi the Lean, as has been said before. After that Ketill arrayed his journey west over the sea. Unn, his daughter, and many others of his relations went with him. That same summer Ketill's sons went to Iceland with Helgi, their brother-in-law. Bjorn, Ketill's son, brought his ship to the west coast of Iceland, to Broadfirth, and sailed up the firth along the southern shore, till he came to where a bay cuts into the land, and a high mountain stood on the ness on the inner side of the bay, but an island lay a little way off the land. Bjorn said that they should stay there for a while. Bjorn then went on land with a few men, and wandered along the coast, and but a narrow strip of land was there between fell and foreshore. This spot he thought suitable for habitation. Bjorn found the pillars of his temple washed up in a certain creek, and he thought that showed where he ought to build his house. Afterwards Bjorn took for himself all the land between Staff-river and Lavafirth, and abode in the place that ever after was called Bjornhaven. He was called Bjorn the Eastman. His wife, Gjaflaug, was the daughter of Kjallak the Old. Their sons were Ottar and Kjallak, whose son was Thorgrim, the father of Fight-Styr and Vermund, but the daughter of Kjallak was named Helga, who was the wife of Vestar of Eyr, son of Thorolf "Bladder-skull", who settled Eyr. Their son was Thorlak, father of Steinthor of Eyr. Helgi Bjolan brought his ship to the south of the land, and took all Keelness, between Kollafirth and Whalefirth, and lived at Esjuberg to old age. Helgi the Lean brought his ship to the north of the land, and took Islefirth, all along between Mastness and Rowanness, and lived at Kristness. From Helgi and Thorunn all the Islefirthers are sprung.