Popular statement frequently used by Formula 1YouTuber Rocketpoweredmohawk. Used to express to swear on something or used as a general indication of anger/frustration
“If Max Verstappen wins the next race and gets his 50th win in a row, I swear down on my nan’s grave, I will be very disappointed”.
Jim: You'll get fucked up this round of Connect Four.
Bob: Nuh-uh, I can pee on one's grave at this game. I've even humiliated a robot in this game.
Jim: Oh shit... O_O