The Collaborative International Dictionary of English v.0.48:

Middleman \Mid"dle*man\, n.; pl. Middlemen.
   [1913 Webster]
   1. An agent between two parties; a broker; a go-between; any
      dealer between the producer and the consumer; in Ireland,
      one who takes land of the proprietors in large tracts, and
      then rents it out in small portions to the peasantry.
      [1913 Webster]

   2. A person of intermediate rank; a commoner.
      [1913 Webster]

   3. (Mil.) The man who occupies a central position in a file
      of soldiers.
      [1913 Webster]