Middangeard is the Old English word that is the main source of J.R.R. Tolkien’s term “Middle-earth.” It referred to the inhabited world or human world in Germanic tradition.
The term is related to Old Norse miðgarðr, commonly rendered as Midgard. Tolkien did not invent the basic expression from nothing; he adapted an old Germanic idea and gave it a central place in his fictional mythology. The spelling “Middle-earth” reflects the modern English form of the concept.
In Tolkien’s writings, Middle-earth is not a separate planet. It is the central inhabited region of Arda, the world containing the lands and histories of his legendarium. The setting changes across the First, Second, and Third Ages, and its geography is only one part of a much larger cosmology.
Readers sometimes interpret “middle” as meaning a location halfway between two places. Tolkien’s use is closer to the older idea of the human world between divine and monstrous realms, filtered through the languages and myths he studied.