furrfu

from Jargon File (4.4.4, 14 Aug 2003)

furrfu
 excl.

   [Usenet; written, only rarely spoken] Written-only equivalent of
   "Sheesh!"; it is, in fact, "sheesh" modified by {rot13}. Evolved in
   mid-1992 as a response to notably silly postings repeating urban myths
   on the Usenet newsgroup alt.folklore.urban, after some posters
   complained that "Sheesh!" as a response to {newbie}s was being
   overused. See also {FOAF}.

from The Free On-line Dictionary of Computing (8 July 2008)

furrfu

   <jargon> Written-only {rot13} "Sheesh!".  "furrfu" evolved in
   mid-1992 as a response to postings repeating urban myths on
   newsgroup news:alt.folklore.urban, after some posters
   complained that "Sheesh!" as a response to {newbies} was being
   overused.

   (1995-10-25)