"Potty is a baby word. Big kids and grown-ups say things like bathroom or restroom. Or toilet. Or commode. Or loo." Okay, except I am pretty sure I have never said the words "commode" or "loo" out loud in my life.
Dear Lu, if it makes you feel more grown up to sound all contrived/Victorian/British, knock yourself out. In fact, henceforth, we'll just call you Loo.