Duck Bottom
One who has a mouf(mouth) like the ass of a ducks, constantly farthing or in this case, endless yapping.
Bill has a bad case of "Duck Bottom".
.Duck Bottom
(1) A mouth that can't shut up. (2) Or one who has a mouth like the butt of a duck, constantly talking, yapping as a ducks butt constantly farts.
Bill has a bad case of .duck bottom