It stands for "INTentional feeding" and it is used in videogames (mainly League of Legends).
Most possibly started from
the League of Legends banned toxic streamer
tyler1 because of his ''INT list'' where he was writing down players who were playing bad, intentionally feed, intentionally ruin the game and so on.
Another case would be from his famous ''Running it down mid'' where he runs down the midlane (as the phrase says) and
suicides, giving free kills to the enemy team after getting frustrated about a certain event/player in the match he is playing.