The Collaborative International Dictionary of English v.0.48:

Motivity \Mo*tiv"i*ty\, n. [See Motive, n.]
   1. The power of moving or producing motion.
      [1913 Webster]

   2. The quality of being influenced by motives. [R.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

motivity
    n 1: the power or ability to move [syn: locomotion, motive
         power, motivity]