The Collaborative International Dictionary of English v.0.48:

Proficience \Pro*fi"cience\, Proficiency \Pro*fi"cien*cy\, n.
   The quality of state of being proficient; advance in the
   acquisition of any art, science, or knowledge; progression in
   knowledge; improvement; adeptness; as, to acquire proficiency
   in music.
   [1913 Webster]