Berserk is from Old Norse Berserkr, either "bear coat"; or "bare coat" i.e. unarmoured & (popularly) even shirtless. I would love to know why you think it's from Indonesia, Robin!

I suspect Jeremiah is right & you're confusing it with amok, Malay " rushing in a frenzy" according to the OED.

OED also gives kung fu as deriving from gong "merit" & fu "master", by way of variation!