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

system mangler
 n.

    Humorous synonym for ?system manager?, poss. from the fact that one major
    IBM OS had a root account called SYSMANGR. Refers specifically to a
    systems programmer in charge of administration, software maintenance, and
    updates at some site. Unlike admin, this term emphasizes the technical
    end of the skills involved.


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

system mangler

    A humorous synonym for "system manager", possibly
   from the fact that one major IBM operating system had a
   root account called SYSMANGR.  The term refers specifically
   to a systems programmer in charge of administration, software
   maintenance, and updates at some site.  Unlike admin, this
   term emphasises the technical end of the skills involved.

   [Jargon File]

   (1995-11-10)