The Collaborative International Dictionary of English v.0.48:

Roorback \Roor"back\, Roorbach \Roor"bach\, n.
   A defamatory forgery or falsehood published for purposes of
   political intrigue. [U.S.]
   [1913 Webster]

   Note: The word originated in the election canvass of 1844,
         when such a forgery was published, to the detriment of
         James K. Polk, a candidate for President, purporting to
         be an extract from the "Travels of Baron Roorbach."
         [1913 Webster]