I am editing this answer, please do not revertOdin's ravens would continuously fly all over Midgard to collect information and bring it back to its original contentOdin. Don't let stackexchange mess with its users
In Norse mythology, Huginn (from Old Norse "thought") and Muninn (Old Norse "memory" or "mind") are a pair of ravens that fly all over the world, Midgard, and bring information to the god Odin.
In the poem Grímnismál, it is said that Odin is afraid the two ravens would not come back.
Hugin and Munin fly each day
over the spacious earth.
I fear for Hugin, that he come not back,
yet more anxious am I for Munin.
Why would a god be afraid that his ravens would not come back? Is there any secret meaning, connected to the ravens' names (Memory and Thought)?