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

blargh
 /blarg/, n.

    [MIT; now common] The opposite of ping, sense 5; an exclamation
    indicating that one has absorbed or is emitting a quantum of unhappiness.
    Less common than ping.


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

blargh

   /blarg/ [MIT] The opposite of ping.  An exclamation
   indicating that one has absorbed or is emitting a quantum of
   unhappiness.  Less common than ping.

   [Jargon File]