 The Idisi mentioned in the incantation are generally considered to be valkyries . Rudolf Simek says that " these Idisi are obviously a kind of valkyrie , as these also have the power to hamper enemies in Norse mythology " and points to a connection with the valkyrie name Herfjötur ( Old Norse " army @-@ fetter " ) . Hilda R. Davidson compares the incantation to the Old English Wið færstice charm and theorises a similar role for them both . 
