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

hosed
 adj.

    Same as down. Used primarily by Unix hackers. Humorous: also implies a
    condition thought to be relatively easy to reverse. Probably derived from
    the Canadian slang ?hoser? popularized by the Bob and Doug Mackenzie skits
    on SCTV, but this usage predated SCTV by years in hackerdom (it was
    certainly already live at CMU in the 1970s). See hose. It is also widely
    used of people in the mainstream sense of ?in an extremely unfortunate
    situation?.

    Once upon a time, a Cray that had been experiencing periodic difficulties
    crashed, and it was announced to have been hosed. It was discovered that
    the crash was due to the disconnection of some coolant hoses. The problem
    was corrected, and users were then assured that everything was OK because
    the system had been rehosed. See also dehose.


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

hosed

    A somewhat humorous variant of "down", used
   primarily by Unix hackers.  "Hosed" implies a condition
   thought to be relatively easy to reverse.  It is also widely
   used of people in the mainstream sense of "in an extremely
   unfortunate situation".  The term was popularised by fighter
   pilots refering to being hosed by machine gun fire (date?).
   Usage in hackerdom dates back to CMU in the 1970s or
   earlier.

   "Acronyms and Abbreviations" from UCC, Ireland
   (http://ucc.ie/cgi-bin/acronym) expands it as "Hardware
   Or Software Error Detected", though this is probably a
   back-formation.

   The Jargon File version 4.1.4 1999-06-17 says that it was
   probably derived from the Canadian slang "hoser" (meaning "a
   man, esp. one who works at a job that uses physical rather
   than mental skills and whose habits are slightly offensive but
   amusing").

   One correspondant speculates about an allusion to a hose-like
   body part.

   Once upon a time, a Cray that had been experiencing periodic
   difficulties crashed, and it was announced to have been hosed.
   It was discovered that the crash was due to the disconnection
   of some coolant hoses.  The problem was corrected, and users
   were then assured that everything was OK because the system
   had been rehosed.  See also dehose.

   See also: hose.

   (1999-10-28)