What an asian person does in a toilet, poops, that is.
Caca (poop) sian (asian) = Cacasian
Also, a Caucasian is NOT a white person, it's the Americans fault white people are now called this stupid word, happily it only happens in US and not in the rest of the world (thank god!).
Friend: So, Jin, you did all your cacasian in the toilet?
Jin: Yeah, feels so much better now, let's go play football.