(if you cant tell I nerd out on this one :p)
How Was Middle Earth Concieved
"Middle-earth is ... not my own invention. It is a modernization or alteration ... of an old word for the inhabited world of Men, the oikoumene: middle because thought of vaguely as set amidst the encircling Seas and (in the northern-imagination) between ice of the North and the fire of the South. O. English middan-geard, mediaeval E. midden-erd, middle-erd. Many reviewers seem to assume that Middle-earth is another planet!"
— J.R.R. Tolkien