The Collaborative International Dictionary of English v.0.48:

-ory \-o*ry\suff. [L. -orius: cf. F. -oire.]
   1. An adjective suffix meaning of or pertaining to, serving
      for; as in auditory, pertaining to or serving for hearing;
      prohibitory, amendatory, etc.
      [1913 Webster]

   2. [L. -orium: cf. F. -oire.] A noun suffix denoting that
      which pertains to, or serves for; as in ambulatory, that
      which serves for walking; consistory, factory, etc.
      [1913 Webster] Oryal