ABH, or Accelerated Back Hopping, is a movement mechanic found in source engine games using the HL2 framework. (E.G. HL2, GMod, and I think L4D.) It occurs from a code oversight meant to prevent bunny hopping (another speed gaining mechanic originating around Quake time.) When you land you get a slight backward boost (this isn't 100% accurate I'll expand later.) However, if you're moving backwards, this helps you go faster, having the opposite intended effect.
I'm genuinely gonna read through decomped source and quake code to program it.
