Yggdrasil
/ˈɪgdræsɪl/- Scandinavian Mythology a huge ash tree located at the centre of the earth, with three roots, one extending to Niflheim (the underworld), one to Jotunheim (land of the giants), and one to Asgard (land of the gods)【斯堪的纳维亚神话】乾坤树（据称为一棵位于地球中心的巨大梣树, 有三条根, 分别通往冥府、巨人国和仙宫）。
词源
from Old Norse yg(g)drasill， apparently from Yggr 'Odin' + drasill 'horse'.