Source : Free On-Line Dictionary of Computing

kill file
     
        [{Usenet}] Per-user file(s) used by some {Usenet} reading
        programs (originally {Larry Wall}'s {rn}) to discard summarily
        (without presenting for reading) articles matching some
        particularly uninteresting (or unwanted) patterns of subject,
        author, or other header lines.  Thus to add a person (or
        subject) to one's kill file is to arrange for that person to
        be ignored by one's newsreader in future.  By extension, it
        may be used for a decision to ignore the person or subject in
        other media.  See also {plonk}.
     
        [{Jargon File}]