The term "Middle East" was coined by an American, Captain Alfred Thayer Mahan (author of Influence of Sea Power Upon History, 1660 to 1783), who wrote an article called "The Persian Gulf and International Relations", which was published September, 1902 in the British monthly, The National Review.^1

In this article he wrote,

The Middle East, if I may adopt a term which I have not seen, will some day need its Malta, as well as its Gibraltar; it does not follow that either will be in the Gulf. Naval force has the quality of mobility which carries with it the privilege of temporary absences; but it needs to find on every scene of operation established basis of refit, of supply, and in case of disaster, security. The British Navy should have the facility to concentrate in force, if occasion arise, about Aden, India, and the Gulf.^4

Prior to this excerpt in the same essay Mahan wrote the following, from which we can infer the area he decided to refer to as 'The Middle East':

There is here concentrated therefore commercial and political influence upon both of the two routes, that by land and that by water, from the Mediterranean to India and to the East beyond. There is no occasion in the nature of things that Great Britain, either by concession or compulsion, should share with another State the control which she now has here; but in order to retain it she needs not only to keep the particular protective relations already established with minor local rulers, but further to develop and fortify her commercial interests and political prestige in South Persia and adjacent Mesopotamia.^4

In Thayer's essay, he also uses the term 'Farther East' an impressive 16 times, leading me to believe it had an accepted place in the political parlance of the time. If there existed a Near East and a Farther East, it should not surprise us that the term 'Middle East' was conceived.

Why the term came into fashionable use is due both to Mahan's celebrity and the reputation of London's The Times. Sir Valentine Chirol, foreign editor of The Times and inspired by Mahan's essay,

published twenty successive articles in The Times under the generic title "The Middle Eastern Question", which he later reshaped into a 1903 book, The Middle East Question, or Some Political Problems of Indian Defence. What had been commonly called the Near East, Turkish Asia, or simple the Orient acquired a new name.^1

Numerous other expressions have encompassed or referred to specific places in the area we know as the Middle East. Levant is one, though "Levantine" tends to only refer to coastal areas around the Eastern Mediterranean (this part of the Mediterranean is actually known as the Levantine Sea). In his essay, Thayer included Egypt as being part of the Levant (a term he uses 11 times), though I don't think that was typical. Another common, historical expression was "the Orient", though this included not only the area we know of as the Middle East, but also most of the rest of Asia as well.^3

Today, the geographic designation 'The Middle East' isn't concretely defined. In fact, when reading books on the region, the author will often begin their work by defining what they mean by 'Middle East'. Michael B. Oren, doing this in his own book, explains the modern situation excellently in Power, Faith, and Fantasy:

Writing such a book gives rise to many challenges, the first of which is answering the question, "Where is the Middle East?" Though the term "Middle East" is today almost universally accepted, there is, in fact, no consensus on the region's borders. Many scholars classify Morocco, Tunisia, and Algeria as Middle Eastern countries, while others regard all of North Africa as a separate entity. The Middle Eastern Studies departments at some universities exclude Afghanistan and Pakistan from their scope, but other programs cover the Cacusus [sic] and Southwest Asia. Disagreements over the parameters of the area deepen the further on retreats into history. Historians differ over whether a discussion of the eighteenth-century Middle East should incorporate Ottoman Bulgaria and Greece or whether these provinces belonged to a discrete an nebulous Near East. Some deny that a Middle East could have existed before 1902, when the term was first employed.^3

[] *Mahan's article can be found by scrolling to page 237 of the linked PDF

^1 - Kingmakers: The Invention of the Modern Middle East, Karl E. Meyer, Shareen Blair Brysac

^2 - The Middle East, Christopher Catherwood

^3 - Power, Faith, and Fantasy: American in the Middle East, 1776 to the Present, Michael B. Oren

^4 - Retrospect and Prospect: Studies in International Relations Naval and Political, A. T. Mahan