The Collaborative International Dictionary of English v.0.48:

Peculium \Pe*cu"li*um\, n. [L. See Peculiar.]
   1. (Rom. Law) The saving of a son or a slave with the
      father's or master's consent; a little property or stock
      of one's own; any exclusive personal or separate property.
      --Burrill.
      [1913 Webster]

   2. A special fund for private and personal uses.
      [1913 Webster]

            A slight peculium only subtracted to supply his
            snuff box and tobacco pouch.          --Sir W.
                                                  Scott.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

PECULIUM, civil law. The savings which were made by a son or slave with the
consent of his father or master. Inst. 2, 9, 1; Dig. 15, 1, 5, 3; Poth. ad
Pand. lib. 50, tit. 17, c. 2, art. 3.
     2. A master is not entitled to the extraordinary earnings of his
apprentice, which do not interfere with his services so as to affect his
master's profits. An apprentice was therefore decreed to be entitled to
salvage in opposition to his master's claim for it. 2 Cranch, 270.