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

Weenix
 /wee'niks/, n.

    1. [ITS] A derogatory term for Unix, derived from Unix weenie.
    According to one noted ex-ITSer, it is ?the operating system preferred by
    Unix Weenies: typified by poor modularity, poor reliability, hard file
    deletion, no file version numbers, case sensitivity everywhere, and users
    who believe that these are all advantages?. (Some ITS fans behave as though
    they believe Unix stole a future that rightfully belonged to them. See ITS
    , sense 2.)

    2. [Brown University] A Unix-like OS developed for tutorial purposes at
    Brown University. See http://www.cs.brown.edu/courses/cs167/weenix.html.
    Named independently of the ITS usage.


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

Weenix

   /wee'niks/ An ITS fan's derogatory term for Unix, derived
   from Unix weenie.  According to one noted ex-ITSer, it is
   "the operating system preferred by Unix Weenies: typified by
   poor modularity, poor reliability, hard file deletion, no file
   version numbers, case sensitivity everywhere, and users who
   believe that these are all advantages".  Some ITS fans
   behave as though they believe Unix stole a future that
   rightfully belonged to them.

   [Jargon File]

   (1995-01-18)