"people of England; the speech of England," Old English Englisc (contrasted to Denisc , Frencisce , etc.), 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 term 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. After 1066, of the population of England (as distinguished from Normans and French), a distinction which lasted only about a generation.
In pronunciation, "En-" has become "In-," but the older spelling has remained. Meaning "English language or literature as a subject at school" is from 1889. As an adjective, "of or belonging to England," from late 13c. Old English is from early 13c.