i goggled why
"Tourette's syndrome is a neurologic disorder than affects the brain's ability to suppress impulsive behavior. Tourette's patients are identified not only by involuntary vocalizations but also by involuntary movements. The vocalizations don't always include "bad" words but may often because of the lack of impulse control."
"It's not always inappropriate words that are used. Many times, it's whatever words are in the person's thoughts. If the person is angry, the words may be a little more harsh. If the y are thinking of what they might want to have for dinner later, they might yell out roasted chicken pot pies! In some cases, the inappropriate words come out simply because it is an outburst, loud and seemingly obnoxious, even though they don't mean to be."