Source : Free On-Line Dictionary of Computing

old fart
     
        Tribal elder.  A title self-assumed with remarkable frequency
        by (especially) {Usenet}ters who have been programming for
        more than about 25 years; often appears in {sig block}s
        attached to {Jargon File} contributions of great archaeological
        significance.  This is a term of insult in the second or third
        person but one of pride in first person.
     
        [{Jargon File}]