Toilet Bowl vs Rice Bowl

All this while I’ve told Jonas to pee pee at “big potty”, I didn’t tell him that is called toilet bowl, I guess “big potty” is easier for him.
One day, I think it is time to correct him with right word. So I told him pee pee at “Toilet Bowl”.
Immediately, he answers me: “No! Is not bowl, is toilet! Bowl is like this (make his hand to describe the pattern of the bowl which use to eat rice)”
Ops! Again I feel every information or word introduce to them must be a correct way. Once they accepted is hard to change their mind.