Hanged man

On the windy days, Odin was hanging from the branch of Yggdrasill, the cosmic World Tree, with a rope around his neck. He was also suffering from a wound that was pierced by his own spear (Gungnir).

Odin remained there for nine days and nine nights. And in the next line [140], Odin learned nine mighty spells, from his grandfather Bolthor, as well as drinking from the precious mead from Odrerir (see Mead of Poetry). The number nine was also significant, in term of symbolism and magic.

From lines 144-145, he not only speaks of carving the runes, but also of sacrifice. It was believed that you could only learn the magic spells from the runes if you were dead. And since it was he who wanted to learn the runes, a sacrifice was needed. Odin paid the sacrifice himself. Which is why he was hanging with a hangman’s noose around his neck, so that is why Odin had acquired the name – Hanga-tyr (“god of the hanged”).

The ninth night coincided with the festival of May Eve (April 30), otherwise known as Walpurgis’ Night, where Odin mastered his ninth and final spell, which the hanged god ritually died. During this final night, all light were extinguished with his supposedly death. It was at this time that chaos and the spirit world reigned supreme and the witchcraft or sorcery is most potent. Odin’s death lasted until midnight, and then light would return to the world. Like the Celtic Beltane or May Day, the night was celebrated with large bonfires lighted around the countryside.

https://www.timelessmyths.com/norse/wisdom.html