member of a Teutonic tribe, Old English, from Latin Angli "the Angles," literally "people of Angul" (Old Norse Öngull), a region in what is now Holstein, said to be so-called for its hook-like shape (see angle (n.)). Or the name might refer to fishing (with hooks) as a main activity of the people, and Proto-Germanic *anguz is said also to have meant "narrow," so it might refer to shallow coastal waters.
People from the tribe there founded the kingdoms of Mercia, Northumbia, and East Anglia in 5c. Britain. Their name, rather than that of the Saxons or Jutes, may have become the common one for the whole group of Germanic tribes because their dialect was the first committed to writing.
"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.