域外之地（The Outer Lands）
As told in The Silmarillion, most of the events of the First Age took place in the land of Beleriand and its environs. In Beleriand were the hidden Elven kingdoms of Doriath, ruled by King Thingol, and Gondolin, founded by Turgon. Also important was the fortress of Nargothrond, founded by the elf Finrod Felagund. In the Blue Mountains to the east were the great dwarf halls of Belegost and Nogrod. Beleriand was split into eastern and western sections by the great river Sirion. In East Beleriand was the river Gelion with its seven tributaries, which defined the Green-elf kingdom of Ossiriand. To the north of Beleriand lay the regions of Nevrast, Hithlum and Dor-lómin, and the Iron Mountains where Morgoth (Melkor) had his fortress of Angband.
the Noldor exiles and other Elves fought long and valiantly against Morgorth, but the First Age nonetheless ended with their irrevocable defeat. The Seige of Angband was broken in F.A. 455 in Dagor Bragollach, the Havens of the Falas were ruined in F.A. 473, Nagothrond was sacked in F.A. 495, Doriath was abandoned in F.A. 506, and Gondolin fell in F.A. 510.
It was the aid Earendil brought from Valinor to Middle-earth which finally defeated Morgorth in the War of Wrath, after which a great part of the Noldorin Elves returned into the West. The violent struggles during the War of Wrath between the Host of the Valar and the armies of Melkor brought about the destruction of Angband, and changed the shape of Middle-earth so that most of Beleriand vanished under the sea.
The peoples called Middle-earth by several names. The Elves called the continent Endóre or Endor in Quenya meaning "middle land"; the Sindarin form was Ennor, also used in the plural ennorath "middle lands, lands of Middle-earth".
Other epithets of the continent were Hither Shores or Hither Lands contrasted to Aman beyond the sea. The Hobbits envisioned Middle-earth as the Wide World and the Outer Lands or Great Lands, since it was so much larger than the continent of Aman.
In ancient Germanic mythology, the world of Men is known by several names, such as Midgard, Middenheim, Manaheim, and Middengeard. The Old English word middangeard descends from an earlier Germanic word and so has cognates in languages related to Old English such as the Old Norse word Miðgarðr from Norse mythology, transliterated to modern English as Midgard.
The term "Middle-earth"; also commonly referred to as "middle-world," was therefore not invented by Tolkien. It is found throughout the Modern English period as a development of the Middle English word middel-erde (cf. modern German Mittelerde), which developed in turn, through a process of folk etymology, from middanġeard (the g being soft, i.e. pronounced like y in its modern descendant "yard"). By the time of the Middle English period, middangeard was being written as middellærd, midden-erde, or middel-erde, indicating that the second element had been reinterpreted, based on its similarity to the word for "earth". The shift in meaning was not great, however: middangeard properly meant "middle enclosure" instead of "middle-earth"; Nevertheless, middangeard has been commonly translated as "middle-earth" and Tolkien followed this course.
Tolkien first encountered the term middangeard in an Old English fragment he studied in 1914:
Hail Earendel, brightest of angels / above the middle-earth sent unto men.
This quote is from the second of the fragmentary remnants of the Crist poems by Cynewulf. The name Éarendel was the inspiration for Tolkien's mariner Eärendil, who set sail from the lands of Middle-earth to ask for aid from the angelic powers, the Valar. Tolkien's earliest poem about Eärendil, from 1914, the same year he read the Crist poems, refers to "the mid-world's rim".
The concept of middangeard was considered by Tolkien to be the same as a particular usage of the Greek word οἰκουμένη - oikoumenē (from which the word ecumenical is derived). In this usage Tolkien says that the oikoumenē is "the abiding place of men"; by this he means it is the physical world in which Man lives out his life and destiny, as opposed to the unseen worlds, like Heaven or Hell.
The term Middle-earth is not, however, used in Tolkien's earliest writings about his created world: writings that date from the early 1920s and which were later published in The Book of Lost Tales (1983-4); nor is the term used in The Hobbit (1937). Tolkien began to use the term "Middle-earth" in the latter part of the 1930s, in place of the earlier terms "Great Lands", "Outer Lands", and "Hither Lands" that he had used to describe this region in his stories. The term "Arda", which refers to the whole world proper, first appeared in The Silmarillion and is a more technical term.The term Middle-earth appears in the drafts of The Lord of the Rings, and the first published appearance of the word "Middle-earth" in Tolkien's works is in the Prologue to that work: "...Hobbits had, in fact, lived quietly in Middle-earth for many long years before other folk even became aware of them." Extended usage
The term Middle-earth has also come[year needed] to be applied as a short-hand for the entirety of Tolkien's legendarium, instead of the technically more appropriate, but lesser known terms Arda which refers to the physical world, and Eä, which refers the physical reality of creation as a whole. Middle-earth is used synonymously as "Arda" as a more recogniseable term for titles such as The Atlas of Middle-earth, even while its subject is beyond the scope of the strict geographical definition of the continent of Endor. Even Christopher Tolkien, while publishing the early drafts and manuscripts of his father, he titled the series The History of Middle-earth, thus equating the term "Middle-earth" with the Legendarium.
Another misuse of the term is the equation of "Middle-earth" with the mapped regions, as seen in the maps to Lord of the Rings. Actually these regions are just the Westlands of Middle-earth, being the north-western portion of the continent. Actually how far Middle-earth extends to the East and the South of the map is unknown. Although Mordor is seen to the south-easter corner of the map, it doesn't mean it belongs to the south-eastern Middle-earth, as there are presumably other lands to the east and south. Karen Fonstad has attempted to reconstruct the entirety of the continent, beyond the Westlands, based on an early map by Tolkien.
Correspondence with the geography of Earth
Tolkien envisioned his stories to take place on our world, in an imaginary historical period and contains the essentials of the northwestern Europe. He did not see his stories to happen on a "remote globe in 'space'" as was the case with other contemporary fiction.
In his earliest drafts of the Legendarium, The Book of Lost Tales, the mythology had more direct connections with our history: Littleheart compares the Fall of Gondolin with the fall of "Bablon", "Ninwi" and "Trui". The Mannish language of Taliska was based on Gothic. Britain was supposed to be former Tol Eressea that was driven towards the Great Lands, with Ireland (the Isle of Iverin) being a part that broke from it. The main character Ottor Wǽfre was intended to be the father of legendary figures Hengest and Horsa who conquered England from the Guidlin, the Brithonin and the Rumhoth. In a later sketch, the Elves were from the region of Luthany before it was pulled out of the mainland and became an island.
Tolkien described the region in which the Hobbits lived as "the North-West of the Old World, east of the Sea", which indicates a connection to England and the north-western region of Europe (the Old World). However, as he noted in private letters, the geographies do not match, and he did not consciously make them match when he was writing:
"As for the shape of the world of the Third Age, I am afraid that was devised 'dramatically' rather than geologically, or paleontologically." "I am historically minded. Middle-earth is not an imaginary world. The name is the modern form (appearing in the 13th century) of midden-erd>middel-erd, an ancient name for the oikoumene, 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 enchantment of distance in time.(Letters, no. 183)
"...if it were 'history', it would be difficult to fit the lands and events (or 'cultures') into such evidence as we possess, archaeological or geological, concerning the nearer or remoter part of what is now called Europe; though the Shire, for instance, is expressly stated to have been in this region...I hope the, evidently long but undefined gap* in time between the Fall of Barad-dûr and our Days is sufficient for 'literary credibility', even for readers acquainted with what is known as 'pre-history'. 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 loveable with the love of blood-kin...(Letters, no. 211)
In another letter, Tolkien made correspondences in latitude (not equations) between Europe and Middle-earth:
"The action of the story takes place in the North-west of 'Middle-earth', equivalent in latitude to the coastlands of Europe and the north shores of the Mediterranean. ... If Hobbiton and Rivendell are taken (as intended) to be at about the latitude of Oxford, then Minas Tirith, 600 miles south, is at about the latitude of Florence. The Mouths of Anduin and the ancient city of Pelargir are at about the latitude of ancient Troy."
He did confirm, however, that the Shire, the land of his Hobbit heroes, was based on England:
"'The Shire' is based on rural England and not any other country in the world..."
In the Prologue to The Lord of the Rings, Tolkien writes: "Those days, the Third Age of Middle-earth, are now long past, and the shape of all lands has been changed..."
The Appendices make several references in both history and etymology of topics 'now' (in modern English languages) and 'then' (ancient languages); The year no doubt was of the same length,¹ [the footnote here reads: 365 days, 5 hours, 48 minutes, 46 seconds.] for long ago as those times are now reckoned in years and lives of men, they were not very remote according to the memory of the Earth. Nodded to both in Appendices and Silmarillion (with supporting information within the HoME series) there are constellations and stars that correspond to the astronomy seen in the northern hemisphere of Earth, including references to the Sun, the Moon, Orion (and his belt), Ursa Major and other planets (described as "stars"; thus Carnil is "Mars").
As for the later legendarium, The Shire not only was conceptually based on rural England but also was expressly stated to be "in this region", "the North-West of the Old World, east of the Sea". Concerning the Shire, Tolkien stated that he intended it to correspond about to the latitude of Oxford, which would result to other Middle-earth locations to correspond (but not necessarily equate with) real-life locations. For instance, Pelargir would fall to about the latitude of ancient Troy. This enabled Andreas Moehn to make more correspondences, and even project the Westlands on a real map of Europe.
On the other hand, Tolkien designed his maps to accomodate the mythology, and was conscious that they did not fit the ancient Earth, as understood by contemporary archeology and historical geology.
Middle-earth has been depicted in a variety of adaptations of Tolkien's work -- the most prominent of which have been the Lord of the Rings and Hobbit film trilogies by Peter Jackson. Middle-earth has appeared in animation in Ralph Bakshi's The Lord of the Rings and Rankin/Bass' adaptations of The Hobbit and The Return of the King. Middle-earth has also been adapted for numerous video games such as The Lord of the Rings Online and War in the North and tabletop role-playing games like the Middle-earth Role Playing system by Iron Crown Enterprises.
Each adaptation has made changes, subtractions, or additions to Tolkien's creation, often adding new locations, creatures, or characters. For the most part, however, the overall geography and style of Tolkien's Middle-earth has been retained.