The Collaborative International Dictionary of English v.0.48:

Underling \Un"der*ling\, n. [Under + -ling.]
   1. An inferior person or agent; a subordinate; a low-ranking
      employee. --Milton.
      [1913 Webster]

   2. Hence, A mean, sorry fellow. --Milton.
      [1913 Webster]

            The fault, dear Brutus, is not in our stars,
            But in ourselves, that we are underlings. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

underling
    n 1: an assistant subject to the authority or control of another
         [syn: subordinate, subsidiary, underling, foot
         soldier]