Hugin and Munin (pronounced “HOO-gin” and “MOO-nin”; Old Norse Huginn, “Thought” and Muninn, “Desire”) are two ravens in Norse mythology who are shamanic helping spirits of the god Odin. The Eddic poem Grímnismál describes them thus, from the perspective of Odin:
Hugin and Munin
Fly every day
Over all the world;
I worry for Hugin
That he might not return,
But I worry more for Munin.
These informants are two of the many sources of Odin’s prodigious wisdom.
Hugin and Munin are semi-autonomous beings who are simultaneously projections or extensions of Odin’s own being. This may sound unusual, but Old Norse literature is rife with just this sort of phenomena. (See Shamanism and The Parts of the Self.) It’s difficult to determine exactly which parts of Odin they correspond to, however. Most helping spirits in animal form are fylgjur, “followers,” attendants who can tell a person with second sight much about the character of the spirit’s owner. However, their names are derived from hugr, “thought,” and munr, “desire,” both of which are distinct parts of the self in their own right. Perhaps they’re avian manifestations of Odin’s hugr and munr, or perhaps they’re fylgjur with the attributes of those other mental faculties. Unfortunately, as fragmentary as the sources for our knowledge of the pre-Christian traditions of the Norse and other Germanic peoples are, that’s just about all we know about Hugin and Munin.
(Note: it’s often claimed that Munin’s name means “Memory,” but for this to be so, it would have to be derived from minni, “memory,” rather than munr, “desire.” The latter, however, is by far the more parsimonious derivation; if the former were the case, we should expect Munin’s Old Norse name to have been something like “Minninn” rather than “Muninn.” Moreover, the above verse from the Grímnismál makes much more sense if Munin’s name means “Desire” rather than “Memory” – for Odin to state that he’s worried about losing his memory in a poem where he recites, in brilliant poetic form, a remarkably systematic description of the entire cosmos in considerable detail would be highly ironic, to say the least.)
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 The Poetic Edda. Grímnismál, verse 20. My translation. The original Old Norse verse reads:
Huginn ok Muninn
fljúga hverjan dag
óumk ek of Hugin,
at hann aftr né komi-t,
þó sjámk meir of Munin.