Source : Webster's Revised Unabridged Dictionary (1913)

Stableboy \Sta"ble*boy`\, Stableman \Sta"ble*man\, n.
   A boy or man who attends in a stable; a groom; a hostler.

Source : WordNet®

stableboy
     n : someone employed in a stable to take care of the horses
         [syn: {stableman}, {groom}, {hostler}, {ostler}]