Heidrun

Heiðrún or Heidrun is a goat in Norse mythology, which consumes the foliage of the tree Læraðr and produces mead for the einherjar. She is described in the Poetic Edda and Prose Edda.

Poetic Edda
In the Poetic Edda Heiðrún is mentioned twice. She is described in the Grímnismál in a way similar to Snorri's description.

Since Snorri quotes other strophes of Grímnismál it seems reasonable to assume that he knew this strophe too and used it as his source for his description of Heiðrún.

In the Hyndluljóð the giantess Hyndla (lit. bitch/she-dog) used the term "Heiðrún" to insult the goddess Freyja. Thorpe and some other translators translated the name straight to "she-goat".

Etymology
The etymology of Heiðrún remains debatable. Anatoly Liberman suggests that Heiðþyrnir, the name of the lowest heaven in Scandinavian mythology (from heið "bright sky"), was cut into two, and on the basis of those halves the names the heavenly goat Heiðrún and of the heavenly stag Eikþyrnir were formed (the element rún ~ run concealed several puns, but it is a common suffix of female names). The etymology of the Modern German name Heidrun is also debatable.

Heiðrún's name is sometimes anglicized Heidrun, Heidhrun, Heithrun, Heidrún, Heithrún or Heidhrún.