The Collaborative International Dictionary of English v.0.48:

Operand \Op"er*and\, n. [From neuter of L. operandus, gerundive
   of operari. See Operate.] (Math.)
   The symbol, quantity, or thing upon which a mathematical
   operation is performed; -- called also faciend.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Faciend \Fa"ci*end\, n. [From neut. of L. faciendus, gerundive
   of facere to do.] (Mach.)
   The multiplicand. See Facient, 2.
   [1913 Webster]