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

flamage
 /flay'm@j/, n.

    [very common] Flaming verbiage, esp. high-noise, low-signal postings to 
    Usenet or other electronic fora. Often in the phrase the usual flamage.
    Flaming is the act itself; flamage the content; a flame is a single flaming
    message. See flame, also dahmum.


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

flame
flamage
flaming

    To rant, to speak or write incessantly and/or
   rabidly on some relatively uninteresting subject or with a
   patently ridiculous attitude or with hostility toward a
   particular person or group of people.  "Flame" is used as a
   verb ("Don't flame me for this, but..."), a flame is a single
   flaming message, and "flamage" /flay'm*j/ the content.

   Flamage may occur in any medium (e.g. spoken, electronic
   mail, Usenet news, web).  Sometimes a flame
   will be delimited in text by marks such as "...".

   The term was probably independently invented at several
   different places.

   Mark L. Levinson says, "When I joined the Harvard student
   radio station (WHRB) in 1966, the terms flame and flamer were
   already well established there to refer to impolite ranting
   and to those who performed it.  Communication among the
   students who worked at the station was by means of what today
   you might call a paper-based Usenet group.  Everyone wrote
   comments to one another in a large ledger.  Documentary
   evidence for the early use of flame/flamer is probably still
   there for anyone fanatical enough to research it."

   It is reported that "flaming" was in use to mean something
   like "interminably drawn-out semi-serious discussions"
   (late-night bull sessions) at Carleton College during
   1968-1971.

   Usenetter Marc Ramsey, who was at WPI from 1972 to 1976,
   says: "I am 99% certain that the use of "flame" originated at
   WPI.  Those who made a nuisance of themselves insisting that
   they needed to use a TTY for "real work" came to be known as
   "flaming asshole lusers".  Other particularly annoying people
   became "flaming asshole ravers", which shortened to "flaming
   ravers", and ultimately "flamers".  I remember someone picking
   up on the Human Torch pun, but I don't think "flame on/off"
   was ever much used at WPI."  See also asbestos.

   It is possible that the hackish sense of "flame" is much older
   than that.  The poet Chaucer was also what passed for a wizard
   hacker in his time; he wrote a treatise on the astrolabe, the
   most advanced computing device of the day.  In Chaucer's
   "Troilus and Cressida", Cressida laments her inability to
   grasp the proof of a particular mathematical theorem; her
   uncle Pandarus then observes that it's called "the fleminge of
   wrecches."  This phrase seems to have been intended in context
   as "that which puts the wretches to flight" but was probably
   just as ambiguous in Middle English as "the flaming of
   wretches" would be today.  One suspects that Chaucer would
   feel right at home on Usenet.

   [Jargon File]

   (2001-03-11)