In every (or almost every) mythology there is a world tree. In Norse mythology, that tree is Yggdrasil. Yggdrasil is the Tree of Life. This great Ash tree spans the existence of the nine worlds and has three long roots. One ends in Jotunheim, another at Urd’s Well where the Gods meet daily, and the third reaches down to Hverglmir.
Yggdrasil is where Odin hung for nine days and nine nights, pierced by His own spear to discover the Runes. Yggdrasil means “Odin’s Horse”. This is because “drasil” means “horse” and Ygg(r) is one of Odin’s many many names. This makes sense to me as well given that the tree does span the nine worlds, so it would seem plausible that a god could use it to get from one world to another.
There is another possible interpretation which I find quite interesting. It says that “ygg” could refer to “yggr” or ‘terror’ though not linked to the Odinic name. This would make the the meaning of Yggdrasil “tree of terror”. Given Odin’s ordeal there that would make a lot of sense for it to bear that name.
Going from that, it could also be said that it’s “Odin’s Tree”. Ygg(r) is one of His names, and He did hang on it.
I really like both interpretations. They both show aspects of Odin and the Tree itself. And both bring about many ideas/cause for meditation.