An expression which grates on my nerves is "potty mouth" - it's very coy and twee - as is its twin, to "go potty" meaning to relieve oneself. It might be cute in a 2YO, but it's a bit ridiculous in a fully-grown adult.

Cheers
JennieG who lets fly with the occasional naughty word occasionally, but doesn't have (heaven forfend!) a potty mouth