Source : Free On-Line Dictionary of Computing

Knights of the Lambda-Calculus
     
        A semi-mythical organisation of wizardly LISP and Scheme
        hackers.  The name refers to a mathematical formalism invented
        by Alonzo Church, with which LISP is intimately connected.
        There is no enrollment list and the criteria for induction are
        unclear, but one well-known LISPer has been known to give out
        buttons and, in general, the *members* know who they are.
     
        [{Jargon File}]