Middle English (n.)
"the middle period in the history of the English language," 1830; see middle (adj.) + English (n.). The term comes from Jakob Grimm's division of Germanic languages into Old, Middle and New in "Deutsche Grammatik" (1819). But for English he retained Anglo-Saxon, then already established, for what we call Old English, and used Old English for what we call early Middle English. Thus his Mittelenglisch, and the Middle English of mid-19th century English writers, tends to refer to the period c. 1400 to c. 1550. The confusion was sorted out, and the modern terminology established (with Middle English for the language from c. 1100 to c. 1500), mostly in the 1870.