rot13

from Jargon File (4.4.4, 14 Aug 2003)
rot13
 /rot ther'teen/, n.,v.

   [Usenet: from `rotate alphabet 13 places'] The simple Caesar-cypher
   encryption that replaces each English letter with the one 13 places
   forward or back along the alphabet, so that "The butler did it!"
   becomes "Gur ohgyre qvq vg!" Most Usenet news reading and posting
   programs include a rot13 feature. It is used to enclose the text in a
   sealed wrapper that the reader must choose to open -- e.g., for
   posting things that might offend some readers, or {spoiler}s. A major
   advantage of rot13 over rot(N) for other N is that it is self-inverse,
   so the same code can be used for encoding and decoding. See also
   {spoiler space}, which has partly displaced rot13 since non-Unix-based
   newsreaders became common.
    
from The Free On-line Dictionary of Computing (8 July 2008)
rot13

   /rot ther'teen/ [{Usenet}: from "rotate alphabet 13 places"],
   v. The simple Caesar-cypher encryption that replaces each
   English letter with the one 13 places forward or back along
   the alphabet, so that "The butler did it!" becomes "Gur ohgyre
   qvq vg!"  Most {Usenet} news reading and posting programs
   include a rot13 feature.  It is used to enclose the text in a
   sealed wrapper that the reader must choose to open - e.g. for
   posting things that might offend some readers, or {spoilers}.
   A major advantage of rot13 over rot(N) for other N is that it
   is self-inverse, so the same code can be used for encoding and
   decoding.

   [{Jargon File}]
    

[email protected]