"typical U.S. middle class community," 1929, from the title of a book published that year ("Middletown: A Study in Contemporary American Culture") by New York sociologists Robert and Helen Lynd, based on information collected 1924-25 in Muncie, Indiana. The U.S. Geological Survey lists 40 towns by that name, not counting variant spellings; see middle (adj.) + town.
in the trading sense, "contractor, negotiator, broker," especially "one who buys merchandise in bulk and sells it in smaller quantities to retailers or other traders," 1795, from middle (adj.) + man (n.). From mid-15c. as the name of some type of workman in wire-making. From 1741 as "one who takes a middle course." In minstrel shows, "the man who sits in the middle of the semicircle of performers and leads the dialogue between songs," by 1870.
"medium in rank, condition, or degree; intermediate," 1540s, from Middle English medlinge "intermediate between two things" (late 14c.), from middle (adj.) + present-participle suffix -ing (2). Used in trade to designate the second of three grades of goods. Hence "only medium, neither good nor bad" (1650s). As an adverb, "tolerably, passably," by 1719.
[T]here is an alarmingly wide chasm, I might almost say a vacuum, between the high-brow, who considers reading either as a trade or as a form of intellectual wrestling, and the low-brow, who is merely seeking for gross thrills. It is to be hoped that culture will soon be democratized through some less conventional system of education, giving rise to a new type that might be called the middle-brow, who will consider books as a source of intellectual enjoyment. ["The Nation," Jan, 25, 1912]
It forms all or part of: amid; intermediate; mean (adj.2) "occupying a middle or intermediate place;" medal; medial; median; mediate; medieval; mediocre; Mediterranean; medium; meridian; mesic; mesial; meso-; meson; Mesopotamia; Mesozoic; mezzanine; mezzo; mezzotint; mid (prep., adj.); middle; Midgard; midriff; midst; midwife; milieu; minge; mizzen; moiety; mullion.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit madhyah, Avestan madiya- "middle," Greek mesos, Latin medius "in the middle, between; from the middle," Gothic midjis, Old English midd "middle," Old Church Slavonic medzu "between," Armenian mej "middle."
1560s, "pertaining to a mathematical mean," from Late Latin medialis "of the middle," from Latin medius "in the middle, between; from the middle," as a noun (medium) "the middle;" from PIE root *medhyo- "middle." Meaning "occupying a middle position, existing between two extremities or extremes" is attested from 1721.