In the Islendingabok (written in the early twelfth century by the Icelandic priest Ari Þorgilsson) Yngvi Tyrkja konungr ‘Yngvi king of Turkey’ appears as the father of Njoror who in turn is the father of Yngvi-Freyr, ancestor of the Ynglings. According to the Skjoldunga saga (a lost epic from 1180 to 1200, saved only partially in other sagas and later translation) Odin came from Asia and conquered Northern Europe. He gave Sweden to his son Yngvi and Denmark to his son Skjoldr. Since then the kings of Sweden were called Ynglings and those of Denmark Skjoldungs.
In the Gesta Danorum (late twelfth century, by Saxo Grammaticus) and in the Ynglinga saga (ca. 1225, by Snorri Sturluson), Freyr is euhemerized as a king of Sweden. In the Ynglinga saga, Yngvi-Freyr reigned in succession to his father Njoror who had-- in this variant -- succeeded Odin. In the Historia Norwegie (written around 1211), in contrast, Ingui is the first king of Sweden, and the father of a certain Neorth, in his turn the father of Froyr: “Rex itaque Ingui, quem primum Swethie monarchiam rexisse plurimi astruunt, genuit Neorth, qui vero genuit Froy; hos ambos tota illorum posteritas per longa secula ut deos venerati sunt. Froyr vero genuit Fiolni, qui in dolio medonis dimersus est"
In the introduction to his Edda (originally composed around 1220) Snorri Sturluson claimed again that Odin reigned in Sweden and relates: “Odin had with him one of his sons called Yngvi, who was king in Sweden after him; and those houses come from him that are named Ynglings.” Snorri here does not identify Yngvi and Freyr, although Freyr occasionally appears elsewhere as a son of Odin instead of a son of Njoror.
In the Skaldskaparmal section of his Prose Edda Snorri brings in the ancient king Halfdan the Old who is the father of nine sons whose names are all words meaning “king” or “lord” in Old Norse, as well as of nine other sons who are the forefathers of various royal lineages, including “Yngvi, from whom the Ynglings are descended”. But rather oddly Snorri immediately follows this with information on what should be four other personages who were not sons of Halfdan but who also fathered dynasties, and names the first of these again as “Yngvi, from whom the Ynglings are descended”. In the related account in the Attartolur “Genealogies” attached to Hversu Noregr byggoist, the name Skelfir appears instead of Yngvi in the list of Halfdan’s sons.
The Ynglinga Saga section of Snorri’s Heimskringla (around 1230) introduces a second Yngvi, son of Alrekr, who is a descendant of Yngvi-Freyr and who shared the Swedish kingship with his brother Alf (see Yngvi and Alf).
Given names and family names
The element Ing(o)- was widely used in Germanic names from an early period; it is not clear whether it originally referred to the Ingaevones, or to the god Yngwi directly. Inguiomer (Inguiomarus) was a relative of the Cheruscian Arminius in the first century. Ingundis was a wife of the Frankish king Chlothar I, whose son Charibert I married an Ingoberga (all in the sixth century). Other combinations such as masculine Inguin, Ingulf, Ingobald, feminine Inghildis, Ingedrudis, Ingoflidis, as well as the short forms Ingo (masculine) and Inga (feminine) are recorded in the early medieval period (seventh to ninth centuries).[6] In Scandinavia and Germany, and areas where these groups settled, names beginning with Ing survived into modern usage, e.g.Ingmar, Ingvar, Ingvild, Ingeborg, Ingrid, Ingegerd and the family name Ingalls.