Bölþorn is used in Gylfaginning (The Beguiling of Gylfi), whereas Bölþor occurs in Hávamál (Sayings of the High One).
Gylfaginning (The Beguiling of Gylfi) mentions in the Prose Edda that Bölþorn is a jötunn, and Bestla's father.
It is often argued that the figure of Bölþorn embodies a traditional relationship with the maternal uncle, a pattern found in Germanic myths and legends alike.
[2][3] According to Orchard, the Roman historian Tacitus (1st c. AD) "had already noted the importance of that particular family tie in Germanic society, and there are numerous examples of the closeness of male figures with their maternal uncles in the literary sources.
"[3] Various scholars have also noted that the unnamed man (Bölþorn's son and Bestla's brother) in Hávamál may be the wise being Mímir.