Inspiration.

Here are three similar stories.

Volsung saga: Regin returns to his brother Sigurd after Fafnir was slain. Sigurd had just killed Fafnir and is going to eat the heart. Regin planned to kill Sigurd after Sigurd had cooked Fáfnir’s heart for him to eat and take all the knowledge for himself. However, Sigurd, having tasted Fáfnir's blood while cooking the heart, gained knowledge of the speech of birds and learned of Regin's impending attack from the "Odinnic" birds' discussion and killed Regin by cutting off his head.

Eddas: Kvasir went up and down the earth to give instruction to men; and when he came upon invitation to the abode of certain dwarves, Fjalar and Galarr, they called him into privy converse with them, and killed him, letting his blood run into two vats and a kettle. The kettle is named Odrerir, and the vats Son and Bodn; they blended honey with the blood, and the outcome was that mead by the virtue of which he who drinks becomes a skald or scholar.
Odrerir is used as a kenning for the mead of poetry, but the literal meaning is "stirrer of inspiration" or "stirrer of fury". Which Makes sense, as it sounds a lot like Wod (fury).

 The theft of the mead of poetry by Odin in the form of the eagle is reminiscent of the theft of the soma drink in the sanskrit tale. The soma drink was stolen from the gods by the god Indra in the form of an eagle. The soma plant used in the soma drink is unknown, but has thoguht to be Amanita Muscaria. Soma is associated with the Warrior god Indra and is drunk before his battle with Vitra. Another candidate for soma has been honey.

The Amanita Muscaria mushroom has been used by siberian shamans to help induce trance, but it creates a range of reactions depending on the person. As with any entheogen, the mind frame one is in determines the effects. I believe the vikings did use the amanita muscaria mushroom to help induce berserker frenzies. I also believe the force Wod that excites one into a frenzy is the same force that inspires poets.

Perhaps Kvasir/Fafnir's blood is the amanita mushroom, it is blood red. The mead of poetry may very well have Amanita in it, possibly making it related to the soma drink. The Soma was drank by Indra before war, possiblly the berserks drank it before war? Just a couple of theories.

Sources/further reading:
Uppsalaonline.com