Universal language

I have a French student now. One Mr. Thomas. I like to think of him as thumnus. You know, of Narnia. Usually I don't have language barrier with my students. They all are more well versed in English than I am. Thomas talks well too. But you never know.
So one day we were discussing the things us humans do, that I'd say not fit for delicate ears. Regular work.
Me: so, there's faeces, urine and sweat.
T: what's that?
Me: faeces?
T: yeah.
Me: umm. You know, human waste.
T: what waste? I don't get it.
Me: Stools?
T: what's stool? Like a seat?
Me: how do I say this. Gaad... Like we go to toilet everyday, u know? Well, some every day. : /
T: like poo?
Me: Yes Thomas! POOP it is! You poo poo head!
The last bit was all in my head.

I am afraid to think what I will do if he starts akibg questions about the rest.