You might be thinking of kapp or kappa, the twitch emotes used to call someone's bluff or accuse them of lying
Dumbass: "Yah dude and I was the best player they had. No one could beat me" Me: "kapp (cap), you were not" or simply "kapp"
Someone by the name creamymilky will forever be a capper and known as one, thy is not innocent and should be striked down by zues and or god
"i'm innocent" - creamymilky
Someone: CAP
as though everyone says that it means lying built different they are very wrong
cap is actually used back in the 1830s when the white nation used slaves but since they didnt want to use capture african people since its obvious they made up the slang cap which actually means capture african people so please use caution infront of black people as they might blow ur head out
white man: ayo nice day inni
black man: yes it is
white man: CAP CAP CAP CAP CAP
black man: .....
white nation: *captures african man*
black man: HELPPPPPPP