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

tree-killer
 n.

    [Sun]

    1. A printer.

    2. A person who wastes paper. This epithet should be interpreted in a broad
    sense; ?wasting paper? includes the production of spiffy but 
    content-free documents. Thus, most suits are tree-killers.

    It is likely that both senses derive their flavor from the epithet
    ?tree-killer? applied by Treebeard the Ent to the Orcs in J.R.R. Tolkien's
    Lord of the Rings. See also elvish, elder days, and especially 
    dead-tree version.


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

tree-killer

    (Sun) 1. A printer.

   2. A person who wastes paper.  This epithet should be
   interpreted in a broad sense; "wasting paper" includes the
   production of spiffy but content-free documents.  Thus,
   most suits are tree-killers.

   This term may derive from J.R.R. Tolkien's "Lord of the
   Rings"

(http://sf.www.lysator.liu.se/sf_archive/sf-texts/SF_resource_guide/sfrgft.htm).
   in which Treebeard the Ent uses it to refer to the orcs'
   master, Saruman of Isengard.  Saruman represents, among other
   things, technology at its most misguided.

   See also: dead tree.

   [Jargon File]

   (1999-11-03)