The Collaborative International Dictionary of English v.0.48:

Pederero \Ped`e*re"ro\, n. [Sp. pedrero, fr. OSp. pedra, Sp.
   piedra, a stone, L. petra, fr. Gr. pe`tra. So named because
   it was at first charged with stones.] (Mil.)
   A term formerly applied to a short piece of chambered
   ordnance. [Written also paterero and peterero.]
   [1913 Webster]