means the fictional continent invented by j.r.r. tolkien as the setting for the hobbit and the lord of the rings, meant to be our own world in a mythic, pre-historic age.

from tolkien lifted the name from old english middangeard, the term anglo-saxons used for the human world, sitting between heaven above and the underworld below — he didn't invent the idea of a middle earth, he just built the best real estate on it.