The Collaborative International Dictionary of English v.0.48:

Muset \Mu"set\, n. [OF. mussette, dim. of musse, muce, a hiding
   place, fr. F. musser, OF. mucier, muchier, to conceal, hide.
   Cf. Micher.]
   A small hole or gap through which a wild animal passes; a
   muse. --Shak.
   [1913 Webster]