In J.R.R. Tolkien’s legendarium, what does the name Middle-earth derive from?

In J.R.R. Tolkien’s legendarium, the name Middle-earth derives from Old English middangeard.

The Old English term referred to the inhabited world, or the human world between heavenly and underworld realms. Tolkien adapted the idea into the name for the central region of Arda, the world in which many of his stories take place.

The term is therefore not simply a modern description meaning the middle of a planet. It reflects Tolkien’s philological practice of reshaping historical words and concepts for his invented mythology.

Readers sometimes connect Middle-earth directly to the Norse name Midgard. Norse mythology was an influence, but Tolkien’s English form is especially linked to the Old English middangeard tradition.