Midgard, "the middle enclosure", is the world of human beings in Norse cosmology, and its name states its place: it lies in the middle of the Nine Worlds, between the divine realm of Asgard above and the shadowed underworlds below, joined to Asgard by the rainbow bridge Bifrost. The Eddas describe its making from the body of the primordial giant Ymir, slain by Odin and his brothers: from his flesh they formed the earth, from his blood the seas, from his bones the mountains, from his skull the dome of the sky, and, crucially, from his eyebrows they built the wall of Midgard to fence the world of men against the giants of Jotunheim outside.
The human world is thus a protected enclosure carved out of chaos and defended against it. Around it, in the encircling ocean, lies coiled the World Serpent Jormungandr, so vast it grips its own tail and rings the whole of Midgard, and at Ragnarok the serpent will rise from the sea, and Thor will kill it and be killed by its venom in the same encounter. Midgard is, in short, the fragile middle ground of the Norse cosmos: the ordered home of humanity, walled against the wild, ringed by a monster, and destined to be unmade and, the sources add, reborn.