tunafish

tunafish n.  In hackish lore, refers to the mutated
   punchline of an age-old joke to be found at the bottom of the
   manual pages of `tunefs(8)' in the original {BSD} 4.2
   distribution.  The joke was removed in later releases once
   commercial sites started using 4.2.  Tunefs relates to the
   `tuning' of file-system parameters for optimum performance, and
   at the bottom of a few pages of wizardly inscriptions was a `BUGS'
   section consisting of the line "You can tune a file system, but
   you can't tunafish".  Variants of this can be seen in other BSD
   versions, though it has been excised from some versions by
   humorless management {droid}s.  The [nt]roff source for SunOS
   4.1.1 contains a comment apparently designed to prevent this:
   "Take this out and a Unix Demon will dog your steps from now until
   the `time_t''s wrap around."