I’m currently reading “Runes et Chamanisme” by Jean Vertemont & Jean-Gabriel Foucaud. They have an interesting theory about the origin of the Runic signs that seems to support & reinforce their divine and otherworldly origin. There was already some knowledge of the cosmos and the astral bodies at the time, a knowledge that came originally from India, Greece, and Iran (but is particularly close to the Vedic system).
When considering the origin of the Runes themselves, you will stumble again and again on the text from the Havamal in which Odin describes than he hung upside down from the cosmic tree for 9 days and 9 nights, without food or water. Privations and improper blood circulation/blood oxygenation will surely trigger altered mind states and even hallucinations. The upside down posture is the same one that the one pictured on the Hanged Man card in the Tarot. An in-between state of mind and of being, literally.
But hanging upside down caused Odin to gaze at the Heavens: planets, stars, constellations and more…And the shapes of the Runes that he saw where the constellations painted in the night sky (combined with some knowledge of astronomy): Fehu looks like the Pleiades, Laguz looks like Pegasus…etc. There seems to be an astral counterpart for each of the 24 Runes of the Elder Futhark.
And who was Odin? He was a wise man, a shaman who shared his findings and knowledge with the rest of Humanity. And through his deeds, he became hallow and, over time, found his place at the head of the Northern Pantheon.
If you wish to learn more on the topic of Runic Astronomy, I suggest that you head over to the Runic Sky (though his findings may not be quite the same than the ones I’m discovering in my French book).