Yggdrasil (from Old Norse Yggdrasill) is an immense and central sacred tree in Norse cosmology. Around it exists all else, including the Nine Worlds. Yggdrasil is attested in the Poetic Edda compiled in the 13th century from earlier traditional sources, and in the Prose Edda compiled in the 13th century by Snorri Sturluson. In both sources, Yggdrasil is an immense ash tree that is central to the cosmos and considered very holy. The gods go to Yggdrasil daily to assemble at their traditional governing assemblies. The branches of Yggdrasil extend far into the heavens, and the tree is supported by three roots that extend far away into other locations; one to the well Urðarbrunnr in the heavens, one to the spring Hvergelmir, and another to the well Mímisbrunnr. Creatures live within Yggdrasil, including the dragon Níðhöggr, an unnamed eagle, and the stags Dáinn, Dvalinn, Duneyrr and Duraþrór. Scholars generally consider Hoddmímis holt, Mímameiðr, and Læraðr to be other names for the tree. The tree is an example of sacred trees and groves in Germanic paganism and mythology, and scholars in the field of Germanic philology have long discussed its implications. Etymology The generally accepted meaning of Old Norse is "Odin's horse", meaning "gallows". This interpretation comes about because means "horse" and is one of Odin's many names. The Poetic Edda poem describes how Odin sacrificed himself by hanging from a tree, making this tree Odin's gallows. This tree may have been Yggdrasil. Gallows can be called "the horse of the hanged" and therefore Odin's gallows may have developed into the expression "Odin's horse", which then became the name of the tree. Nevertheless, scholarly opinions regarding the precise meaning of the name vary, particularly on the issue of whether is the name of the tree itself or if only the full term (where Old Norse means "ash tree") refers specifically to the tree. According to this interpretation, would mean the world tree upon which "the horse [Odin's horse] of the highest god [Odin] is bound". Both of these etymologies rely on a presumed but unattested *Yggsdrasill. A third interpretation, presented by F. Detter, is that the name refers to the word ("terror"), yet not in reference to the Odinic name, and so would then mean "tree of terror, gallows". F. R. Schröder has proposed a fourth etymology according to which means "yew pillar", deriving from *igwja (meaning "yew-tree"), and from *dher-