Source : Webster's Revised Unabridged Dictionary (1913)

Groundling \Ground"ling\, n. [Ground + -ling.]
   1. (Zo["o]l.) A fish that keeps at the bottom of the water,
      as the loach.

   2. A spectator in the pit of a theater, which formerly was on
      the ground, and without floor or benches.

            No comic buffoon to make the groundlings laugh.
                                                  --Coleridge.

Source : WordNet®

groundling
     n : in Elizabethan theater: a playgoer in the cheap standing
         section