When the Aesir and the Vanir stopped fighting, they chewed up berries, spat them into a big pot, and created Kvasir. For some reason, he was very wise, and was the muse of poetry. Then Kvasir was murdered by a couple of dwarves, who mixed his blood with honey and made two jars of mead out of it. Then they drank it. This made them very wise. Odin got ahold of the mead, too, so he's very wise. Sometimes, Odin will offer some of his stash to a human. That lucky person is a poet.