Here are some options depending on the context:
* For a young child learning to use the toilet: You could use "paʻa" which means "firm" or "solid" and is often used to describe something that is not loose or runny.
* For a general term for the bathroom: You could use "kauhale", which literally means "house" but is commonly used for bathroom.
* For the act of going to the bathroom: You could use "hele i ka lumi kuke" which literally means "go to the kitchen room" but is a euphemism for going to the bathroom.
It's important to note that using euphemisms is common in Hawaiian culture, so be aware of the context and the audience when choosing your words.