middleman (n.)

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.