This article explores the history of two texts in the fourteenth-century saga compilation Flateyjarbók: Hversu Noregr byggðist and the first chapter of Ættartölur, which together represent a variant of the origin myth Frá Fornjóti ok hans ættmönnum. The article identifies key sources for the intricate genealogies which are used to connect the legendary brothers Nórr and Górr, the first of whom is the creator and eponym of Norway, to prominent figures from Norwegian history, such as the purported unifier Haraldr hárfagri. Based on these sources, it is argued that a thirteenth-century core of this myth was extensively expanded in a co-ordinated effort in the fourteenth century. This expansion emphasized the role of female dynasts in connecting the primordial dynasty of Nórr to the Norwegian ruling line, which traced its patrilineal descent from the Swedish Ynglingr dynasty. It also wove various key Icelandic progenitors into the offspring of Nórr, giving them a distinguished pedigree among the Norwegian regional aristocracy. It is argued that the emphasis on female dynasts is likely to reflect Norwegian political developments in the first half of the fourteenth century, and several possible dates for the expansion are proposed on this basis. An appendix lists the dynasts found in the tradition and identifies their proposed sources.