Bölþorn was a frost giant in Norse mythology

Norse mythology

Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

. His parentage is unknown. He is the best known as the maternal grandfather of the god Odin

Odin

Odin is a major god in Norse mythology and the ruler of Asgard. Homologous with the Anglo-Saxon "Wōden" and the Old High German "Wotan", the name is descended from Proto-Germanic "*Wodanaz" or "*Wōđanaz"....

.

Attestations

In the Poetic Edda

Poetic Edda

The Poetic Edda is a collection of Old Norse poems primarily preserved in the Icelandic mediaeval manuscript Codex Regius. Along with Snorri Sturluson's Prose Edda, the Poetic Edda is the most important extant source on Norse mythology and Germanic heroic legends, and from the early 19th century...

, it is said about Bölþorn and his children:

Nine mighty songs I got from the son

Of Bolthorn, Bestla

Bestla

In Norse mythology, Bestla is the mother of the gods Odin, Vili and Vé by way of Borr, the sister of an unnamed being who assisted Odin, and the daughter or, depending on source, granddaughter of the jötunn Bölþorn...

's father;

And a drink I got of the goodly mead

Poured out from Othrorir.>

Bestla is a mother of Odin

Odin

Odin is a major god in Norse mythology and the ruler of Asgard. Homologous with the Anglo-Saxon "Wōden" and the Old High German "Wotan", the name is descended from Proto-Germanic "*Wodanaz" or "*Wōđanaz"....

, Vili and Vé

Vili and Vé

In Norse mythology, Vili and Vé are the brothers of Óðinn , sons of Bestla daughter of Bölþorn and Borr son of Búri:Old Norse Vili means "will"...

 by Borr

Borr

Borr or Burr was the son of Búri and the father of Odin in Norse mythology. He is mentioned in the Gylfaginning, part of Snorri Sturluson's Prose Edda....

. Bölþorn's son could be the wise being Mímir

Mímir

Mímir or Mim is a figure in Norse mythology renowned for his knowledge and wisdom who is beheaded during the Æsir-Vanir War...

.

In the book Gylfaginning

Gylfaginning

Gylfaginning, or the Tricking of Gylfi , is the first part of Snorri Sturluson's Prose Edda after Prologue. The Gylfaginning deals with the creation and destruction of the world of the Norse gods, and many other aspects of Norse mythology...

, it is said that Bölþorn is a giant and father of Bestla.