The Collaborative International Dictionary of English v.0.48:

Mortuary \Mor"tu*a*ry\, n.; pl. Mortuaries. [LL. mortuarium.
   See Mortuary, a.]
   1. A sort of ecclesiastical heriot, a customary gift claimed
      by, and due to, the minister of a parish on the death of a
      parishioner. It seems to have been originally a voluntary
      bequest or donation, intended to make amends for any
      failure in the payment of tithes of which the deceased had
      been guilty.
      [1913 Webster]

   2. A burial place; a place for the dead.
      [1913 Webster]

   3. A place for the reception of the dead before burial; a
      deadhouse; a morgue.
      [1913 Webster]

   4. A funeral home.
      [PJC]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

MORTUARIES, Eng. law. These are a sort of ecclesiastical heriots, being a
customary gift claimed by and due to the minister, in many parishes, on the
death of the parishioner. 2 Bl. Com. 425.