"At this point three separate and possibly related conclusions may be stated. First, the toponym Járnviðr operates as part of a central-place complex geographically situated in both a historical context (on the southern Jutland peninsula) and in a mythological context (in as much as Járnviðr is in the east relative to the settlement known as Miðgarðr on/near Iðavõllr). Second, the toponym Járnviðr exhibits a conceptual association between two important resources in smithing practices, namely bog iron and wood or fuel. This semantic association is parallel to the settlement activities and topographic associations connected to the historical toponyms Jarnwith, Isarnho and Jerrishoe. Third, according to Vsp 40 and multiple corroborating sources the Járnviðr site is somehow associated with female denizens, or vice versa, one of whom is responsible for the creation or fostering, birth or raising, of a specifically destructive type of being í trollz hami, “in [the] shape of a troll” (Vsp 40.8). In conclusion, the mythological toponym Járnviðr is both part of a generally Norse concept of bog iron processing in settlement contexts and it is also part of an eminently local tradition of bog iron smelting and other crafting and trading activities on the southern Jutland peninsula around Hedeby."
-Leif Einarson, from "Re-forging the smith: an interdisciplinary study of smithing motifs in Völuspá and Völundarkviða" (2011)