also mid-term, "in the middle of a term" in any sense, from mid (adj.) + term (n.). By 1879 in reference to gestation; 1888 of college semesters (midterm examination is by 1900; student slang shortening midterms for these is by 1903). By 1891 in reference to U.S. congressional elections held in the middle of a four-year presidential term.
also mid-day, "the middle of the day," from Old English middæg "midday, noon," contracted from midne dæg; see mid (adj.) + day. Similar formation in Old Frisian middei, Dutch middag, Old High German mittitag, German Mittag, Old Norse miðdagr. As an adjective, "of or pertaining to midday," from early 14c.
Old English mid-weg "the middle of a way or distance;" see mid (adj.) + way (n.). Meaning "central avenue of a fairground" is first recorded 1893, American English, in reference to the Midway Plaisance of the Worlds Columbian Exposition held that year in Chicago. The Pacific island group is so called for being midway between America and Asia. The great naval battle there was fought June 4-7, 1942. As an adverb from late Old English.