The Collaborative International Dictionary of English v.0.48:

Boxen \Box"en\ (b[o^]ks"'n), a.
   Made of boxwood; pertaining to, or resembling, the box
   (Buxus). [R.]
   [1913 Webster]

         The faded hue of sapless boxen leaves.   --Dryden.
   [1913 Webster]

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

boxen
 /bok'sn/, pl.n.

    [very common; by analogy with VAXen] Fanciful plural of box often
    encountered in the phrase ?Unix boxen?, used to describe commodity Unix
    hardware. The connotation is that any two Unix boxen are interchangeable.


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

boxen

   /bok'sn/ (By analogy with VAXen) A fanciful plural of box
   often encountered in the phrase "Unix boxen", used to describe
   commodity Unix hardware.  The connotation is that any two
   Unix boxen are interchangeable.

   [Jargon File]

   (1994-11-29)