The Jargon File (version 4.4.7, 29 Dec 2003):

fool file
 n.

    [Usenet] A notional repository of all the most dramatically and abysmally
    stupid utterances ever. An entire subgenre of sig blocks consists of the
    header ?From the fool file:? followed by some quote the poster wishes to
    represent as an immortal gem of dimwittery; for this usage to be really
    effective, the quote has to be so obviously wrong as to be laughable. More
    than one Usenetter has achieved an unwanted notoriety by being quoted in
    this way.


The Free On-line Dictionary of Computing (30 December 2018):

fool file

    A term found on Usenet for a notional repository of
   all the most dramatically and abysmally stupid utterances
   ever.  An entire subgenre of sig blocks consists of the
   header "From the fool file:" followed by some quote the poster
   wishes to represent as an immortal gem of dimwittery; for this
   usage to be really effective, the quote has to be so obviously
   wrong as to be laughable.  More than one Usenetter has
   achieved an unwanted notoriety by being quoted in this way.

   (2001-01-05)