Bottom Milk

Sam has never had a compact bowel movement in his life.  Michael and I decided that we would give lactose free milk a try.  We told Sam that he got him some special milk that I will help him have an easier time going to the bathroom.  Sam voiced his understanding.  

Yesterday, Sam asked me if he could have some "bottom milk."

We was so serious; he wasn't trying to be funny.  He legitimately thinks that lactose free milk is called "bottom milk."