Járnviðr

In Norse mythology, Járnviðr (Old Norse "Iron-wood") is a forest located east of Midgard, inhabited by troll women who bore giantesses and giant wolves. Járnviðr is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson.

Járnvid is mentioned in Völuspá (40):

The one that will be "the snatcher of the moon" is Mánagarmr (or Hati), and the "old woman" may refer to Fenrir's mother Angrboða.

Snorri Sturluson quotes this stanza and expands it in his Gylfaginning (12):

The form "Járnviðjur" ("Ironwoodite") is nowhere else to be found, but in singular, Járnviðja is listed in the þulur as a troll-wife, and in 10th century skald Eyvindr Skáldaspillir's Háleygjatal (2), referring to the goddess Skaði.

...
Wikipedia