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

baz
 /baz/, n.

    1. [common] The third metasyntactic variable ?Suppose we have three
    functions: FOO, BAR, and BAZ. FOO calls BAR, which calls BAZ....? (See also
    fum)

    2. interj. A term of mild annoyance. In this usage the term is often drawn
    out for 2 or 3 seconds, producing an effect not unlike the bleating of a
    sheep; /baaaaaaz/.

    3. Occasionally appended to foo to produce ?foobaz?.

    Earlier versions of this lexicon derived baz as a Stanford corruption of 
    bar. However, Pete Samson (compiler of the TMRC lexicon) reports it was
    already current when he joined TMRC in 1958. He says ?It came from Pogo.
    Albert the Alligator, when vexed or outraged, would shout ?Bazz Fazz!? or ?
    Rowrbazzle!? The club layout was said to model the (mythical) New England
    counties of Rowrfolk and Bassex (Rowrbazzle mingled with (Norfolk/Suffolk/
    Middlesex/Essex).?


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

baz

   /baz/ The third metasyntactic variable "Suppose we have
   three functions: FOO, BAR, and BAZ.  FOO calls BAR, which
   calls BAZ..." (See also fum).  Occasionally appended to
   foo to produce "foobaz".

   Early versions of the Hacker Jargon dictionary derived "baz"
   as a Stanford corruption of bar.  However, Pete Samson
   (compiler of the TMRC lexicon) reports it was already
   current when he joined TMRC in 1958.  He says "It came from
   "Pogo".  Albert the Alligator, when vexed or outraged, would
   shout "Bazz Fazz!" or "Rowrbazzle!"  The club layout was said
   to model the (mythical) New England counties of Rowrfolk and
   Bassex (Rowrbazzle mingled with Norfolk/Suffolk/Middlesex/
   Essex)."

   [Jargon File]

   (2008-06-30)