The Collaborative International Dictionary of English v.0.48:

black hole \black" hole`\
   A dungeon or dark cell in a prison; a military lock-up or
   guardroom; -- now commonly with allusion to the cell (the
   Black Hole) in a fort at Calcutta (called the Black Hole of
   Calcutta), into which 146 English prisoners were thrust by
   the nabob Suraja Dowla on the night of June 20, 1765, and in
   which 123 of the prisoners died before morning from lack of
   air.
   [1913 Webster]

         A discipline of unlimited autocracy, upheld by rods,
         and ferules, and the black hole.         --H. Spencer.
   [1913 Webster]

   2. (Physics, Astron.) An astronomical object whose mass is so
      condensed that the gravitational force does not allow
      anything, even light, to escape from its outer limit (the
      event horizon). The existence of such objects was first
      proposed from theoretical considerations. Because light
      cannot escape from such objects, they have not yet been
      detected with certainty (1998), but several "candidates"
      have been observed whose properties strongly suggest that
      they are black holes. Some theorists suggest that the
      centers of many galaxies may have large black holes at
      their cores. See also escape velocity.
      [PJC]

   3. [from the astronomical black hole.] a place into which
      things may enter, but can never emerge. [Fig., Jocose] "He
      was so disorganized his office was a black hole."
      [PJC]

WordNet (r) 3.0 (2006):

Black Hole of Calcutta
    n 1: a dungeon (20 feet square) in a fort in Calcutta where as
         many as 146 English prisoners were held overnight by Siraj-
         ud-daula; the next morning only 23 were still alive