(Odin the hanged man had one eye.)

The price of drinking from the well was not small. Odin gave up one of his eyes so he could drink from the Well of Knowledge.

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It is interesting that the origin of sacrificing by hanging victim had existed and written some hundreds of years before the Havamal was written. According to Tacitus, a Roman historian (fl. AD 100), he recorded an older tradition practised by the Cimbri, an ancient Germanic tribe. The Cimbri sacrificed their victims to Wodan (Woden), the Germanic form of Odin (some called him by his Roman name, Mercury), by hanging their victims over a cauldron. The priestess then cut the hanged victims’ throats, so that they would bleed in the cauldron, before their bodies were thrown into sacred lakes.

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