Middle English n.

Old English middel, "equally distant from extremes or limits; intermediate," from Proto-West Germanic *midla- (source also of Old Frisian middel, Old Saxon middil, Middle Low German, Dutch middel, Old High German mittil, German mittel), from Proto-Germanic *medj, from PIE root *medhyo- "middle."

Middle finger "the third finger" (counting the thumb as the first)  so called from late Old English. Middle school is attested from 1838, originally "middle-class school, school for middle-class children;" the sense in reference to a school for grades between elementary and high school is from 1960. Middle management, the level below senior management, is by 1941.

Middle-of-the-road in the figurative sense is attested from 1894, originally political; edges of a dirt road can be washed out and thus are less safe, but the notion here probably is of the middle as "less exposed to ambush." Middle way in the figurative sense of "path of moderation" is from c. 1200. Middle ground as "place of moderation or compromise between extremes" is by 1961. Middle-sized "of medium size" is by 1620s.

In U.S. history, the Middle States (1784) were those between New England and the South (New York, New Jersey, Pennsylvania, Delaware). Middle America for "the 'silent majority,' the generally conservative middle regarded as a homogeneous group" is by 1968.

"the people of England; the speech of England," noun use of Old English adjective Englisc (contrasted to Denisc, Frencisce, etc.), "of or pertaining to the Angles," from Engle (plural) "the Angles," the name of one of the Germanic groups that overran the island 5c., supposedly so-called because Angul, the land they inhabited on the Jutland coast, was shaped like a fish hook (see angle (n.)). The use of the word in Middle English was reinforced by Anglo-French Engleis. Cognates: Dutch Engelsch, German Englisch, Danish Engelsk, French Anglais (Old French Engelsche), Spanish Inglés, Italian Inglese.

Technically "of the Angles," but Englisc also was used from earliest times without distinction for all the Germanic invaders — Angles, Saxon, Jutes (Bede's gens Anglorum) — and applied to their group of related languages by Alfred the Great. "The name English for the language is thus older than the name England for the country" [OED]. After 1066, it specifically meant the native population of England (as distinguished from Normans and French occupiers), a distinction which lasted about a generation. But as late as Robert of Gloucester's "Chronicle" (c. 1300) it still could retain a sense of "Anglian" and be distinguished from "Saxon" ("Þe englisse in þe norþ half, þe saxons bi souþe").

... when Scots & others are likely to be within earshot, Britain & British should be inserted as tokens, but no more, of what is really meant [Fowler]

In pronunciation, "En-" has become "In-," perhaps through the frequency of -ing- words and the relative rarity of -e- before -ng- in the modern language. A form Inglis is attested from 14c. and persisted in Scotland and northern England, and Ingland and Yngelond were used for "England" in Middle English, but the older spelling has stood fast. Meaning "English language or literature as a subject at school" is from 1889.

1701 as a typeface, from old + English. It was used to meaning "the Anglo-Saxon language before the Conquest, old-fashioned or archaic English" in a c. 1200 account of the native (as opposed to Latin) month names, but the modern linguistic use is from 19c. (see Middle English).