[Gothmog]

We have concluded that Tolkien got his name from the old Nordic/Old English word for the world-Midgård/Midgard/Middanġeard etc. But the original question was: why middle-earth. This is only one half of the explanation, we still haven't discussed why he used the old Norse word for the world. One reason may be that he simply liked the old Norse tales and the mythology, but I don't find it very likely that he used that word out of coincidence. Simply taking a word he liked seems to simple.

Considering his skills in language and his interest in Norse myth's, we can assume that he knew the original meaning of the word and Middle-Eart implies that it's in the middle of something. So what is it in the middle of?

- Heaven (Valinor) and hell (the Void) as Kath proposed? (This is also close to the Norse meaning of the word) I dont' know about that one. The Void doesn't have that hellish look in my imagination, it's just the empty space outside the world.

- In the geographic middle? Maybe, the landmass surrounded by oceans, in the middle of the world.

- Middle=centre? Meaning in the centre of the world. Middle earth shows a geocentric conception to the world, as opposed to our own heliocentric picture of the world. And besides, this is the centre of the creation; this is where the Valar lives and this is what Eru created with the help of the song of Ainur. The view of the world in centre of everything, both in space and in the creation, was the dominating view in the "real" world for a long time, until science was evolved to the point when we realized this was in fact wrong (at least the geocentric picture). Could that be the solution, to name this pre-advanced-science world Middle Earth because the inhabitants believed that they were in the middle? And maybe thery were?

- Or, this was a word Tolkien liked without deeper meaning?

I don't know. But whatever the answer is, the fact that the concept Middle Earth already existed can't be neglected and of course played a role when Tolkien selected the name.