The Collaborative International Dictionary of English v.0.48:

Somnipathy \Som*nip"a*thy\, n. [L. somnus sleep + Gr. ? a
   suffering of the body, fr. ?, ?, to suffer.]
   Sleep from sympathy, or produced by mesmerism or the like.
   [Written also somnopathy.]
   [1913 Webster] Somnolence