In the center of the 9 worlds is the great tree Yggdrasil . Th | .

In the center of the 9 worlds is the great tree Yggdrasil . The upper branches of Yggdrasil surround  Asgard , the home and fortress of the Aesir gods.
Yggdrasil grows out of the 'Urd's Well', a pool whose unfathomable depths 'contains many of the most powerful forces and beings in the cosmos. Among these beings are the 'Norns', three shrewd maidens who create the fates of all beings. One of the main techniques they use to shape fate is carving runes on the trunk of Yggdrasil. The symbols carry these intentions throughout the tree, affecting everything in the 'Nine Worlds'.
Wotan watched the Norns from his chair in Asgard and he directed his will to the task of knowing the runes.
Since the native home of the runes is in the Pit of Urd with the Norns, and since the runes reveal themselves to none but those who prove themselves worthy of such terrifying insights and abilities, Wotan hanged himself from a branch of Yggdrasil , pierced himself with his spear, and looked down into the murky waters below. He forbade any of the other gods from granting him the slightest help, not even a sip of water. And he looked down, and he looked down, and he called the runes.
He survived in this state, teetering on the precipice that separates the living from the dead, for no less than nine days and nights. At the end of the ninth night, he finally realized shapes in the depths: the runes! They accepted his sacrifice and showed themselves to him, revealing not only their forms but also the secrets that lie within them. Having fixed this knowledge in his formidable memory, Wotan ended his ordeal with a cry of exultation.

After revealing the Runes to Wotan he gave them as a gift to his descendants in Midgard as we know to this day.

@schwarzekorps