The Collaborative International Dictionary of English v.0.48:

Dimity \Dim"i*ty\, n. [Prob. fr. Gr. ? of double thread, dimity;
   di- = di`s- twice + ? a thread of the warp; prob. through D.
   diemet, of F. dimite, d['e]mitte. Cf. Samite.]
   A cotton fabric employed for hangings and furniture
   coverings, and formerly used for women's under-garments. It
   is of many patterns, both plain and twilled, and occasionally
   is printed in colors.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dimity
    n 1: a strong cotton fabric with a raised pattern; used for
         bedcovers and curtains