From flame + -fest.
flamefest (plural flamefests)
- (Internet slang, dated) Large-scale mutual flaming. [from 1985]
1985 June 26, Les Earnest, “Finger follies and the value of anonymity”, in fa.human-nets[1] (Usenet):For example, if I am engaged in a flamefest on an Arpanet discussion group, I sometimes check on my target until he appears to have logged out and gone to bed.