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

overflow pdl

    The place where you put things when your pdl is
   full.  If you don't have one and too many things get pushed,
   you forget something.  The overflow pdl for a person's memory
   might be a memo pad.  This usage inspired the following
   doggerel:

    Hey, diddle, diddle
    The overflow pdl
      To get a little more stack;
    If that's not enough
    Then you lose it all,
      And have to pop all the way back.
   			       --The Great Quux

   The term pdl seems to be primarily an MITism; outside MIT
   this term is replaced by "overflow stack".

   (2008-05-30)