"Where is this from?" - Quote-search

[Eorl of Rohan]

I, too, remember reading about it somewhere but I can't remember where either
I suspect I read it in an introductory essay that precedes one of Tolkien's works... Good luck with finding out where it's from!

[Inziladun]

In answer to your question, Legate, there's also this from Letters:

'Middle-earth', by the way, is not a name of a never-never land without relation to the world we live in....imaginatively this 'history' is supposed to take place in a period of the actual Old World of this planet.

Letter 165

And this:

The theatre of my tale is this earth, the one in which we now live, but the historical period is imaginary.

Letter 183

[Legate of Amon Lanc]

Well, well, great, that looks nice. I am not 100% sure if these are the things I originally had in mind, but I definitely got in the answers more than I hoped for Thanks to everybody once again... Still, if anybody came up with something more, you can let me know... otherwise, this thread is open for anybody who would feel in similarly dire need as me. (But for the sake of not spamming around and also for honing your own research skills, I suggest you always try to first find it by yourselves! )

[Guinevere]

Here is the quote from letter #165 that Inziladun gave, a bit more extensive:

"Middle-earth", by the way, is not a name of a never-never land without relation to the world we live in. It is just a use of Middle English middel-erde (or erthe),altered from Old English Middangeard: the name for the inhabited lands of Men "between the seas". And though I have not attempted to relate the shape of the mountains and land-masses to what geologists may say or surmise about the nearer past, imaginatively this "history" is supposed to take place in a period of the actual Old World of this planet.

and the quote from letter #183 also more extensive:

I am historically minded. Middle-earth is not an imaginary world. The name is the modern form (appearing in the 13th century and still in use) of midden-erd> middel-erd, an ancient name for the abiding place of Men, the objectively real world, in use specifically opposed to imaginary worlds (as Fairyland) or unseen worlds (as Heaven or Hell). The theatre of my tale is this earth, the one in which we now live, but the historical period is imaginary. The essentials of that abiding place are all there (at any rate for inhabitants of N.W. Europe), so naturally it feels familiar, even if a little glorified by the enchantment of distance in time.

And here is a quote from letter #211

I have, I suppose, constructed an imaginary time, but kept my feet on my own mother earth for place. I prefer that to the contemporary mode of seeking remote globes in "space". However curious, they are alien, and not lovable with the love of blood-kin.
Middle-earth is not my own invention. It is a modernization or alteration of an old word for the inhabited world of Men: middle because thought of vaguely as set amidst the encircling Seas and (in the northern imagination ) between the ice of the North and the fire of the South.

I hope you are now satisfied, Legate!
(I remembered that I had looked up these quotes some years ago for a German discussion forum, so I could just copy-paste them now.)

[Legate of Amon Lanc]

Ah, wonderful. Thanks, Guinevere! Actually I think the #183 now in its full sounds a bit like the thing I had in mind originally, though still I am not sure. But great, thanks for your help