GTFOH comes from MKSM, the abbreviation fans use for Mortal Kombat: Shaolin Monks, the 2005 action-adventure spin-off that let players fight through Outworld as Liu Kang and Kung Lao. Short voice clips from older games like this spread easily on soundboards because they are brief, expressive and understood without context. Online, the line outgrew the game scene it came from and became a general shorthand for rejecting nonsense, which keeps it useful long after release.