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

wirehead
 /wi:r'hed/, n.

    [prob.: from SF slang for an electrical-brain-stimulation addict]

    1. A hardware hacker, especially one who concentrates on communications
    hardware.

    2. An expert in local-area networks. A wirehead can be a network software
    wizard too, but will always have the ability to deal with network hardware,
    down to the smallest component. Wireheads are known for their ability to
    lash up an Ethernet terminator from spare resistors, for example.


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

wirehead

    /wi:r'hed/ (Probably from SF slang for an electrical
   brain-stimulation addict) 1. A hardware hacker, especially one
   who concentrates on communications hardware.

   2. An expert in local-area networks.  A wirehead can be a
   network software wizard too, but will always have the ability
   to deal with network hardware, down to the smallest component.
   Wireheads are known for their ability to lash up an Ethernet
   terminator from spare resistors, for example.

   [Jargon File]

   (1995-02-28)