"confused conflict among many persons," 1640s, from French mêlée, from Old French meslee "brawl, confused fight; mixture, blend" (12c.), noun use of fem. past participle of mesler "to mix, mingle" (see meddle). See also medley. Borrowed in Middle English as melle but it was lost and then reborrowed 17c.
also *meig-, Proto-Indo-European root meaning "to mix."
It forms all or part of: admix; admixture; immiscible; mash; meddle; medley; melange; melee; mestizo; metis; miscegenation; miscellaneous; miscible; mix; mixo-; mixture; mustang; pell-mell; promiscuous.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit misrah "mixed;" Greek misgein, mignynai "to mix, mix up, mingle; to join, bring together; join (battle); make acquainted with;" Old Church Slavonic mešo, mesiti "to mix," Russian meshat, Lithuanian maišau, maišyti "to mix, mingle," Welsh mysgu "to mix."