Green’s Dictionary of Slang

to break wind; also in fig. use, to speak abusively.

1937		Duckett & Staple ‘Double Feature’ in N.Y. Age 10 July 7/1: This copper-coloured community won’t get the first whiff of anything like adequate police vigilance until it kicks [...] A good old-fashioned beautiful backfiring.
1977		E. Torres Q&A 111: Listen, I am gay. I don’t deny it, but I ain’t no punk. I have backfired on a lot of people on the street who thought, because I was a maricón, they could abuse me.
1983		Neaman & Silver Euphemisms 47: Backfire, A; To Backfire This is a contemporary euphemism clearly based on the analogy between the sound caused by breaking wind and that caused by a car’s incomplete combustion of fuel.
1995		Dly Record (Morristown, NJ) 23 Nov. A15/2: Some euphemisms for passing gas [...] Air biscuit, backfire, bark, barking spider [etc].