Thread drift here, but there's been reference to Tourette Syndrome. It's often misrepresented as causing sufferers to shout out swear words. But what's fascinating is that it doesn't have to be obscenities - vocal tics could comprise any irrelevant words constantly interrupting their speech.

This is a really interesting interview with a woman who says "biscuits" every few words, with an occasional "happy birthday" thrown in. Because she carries on talking as if nothing unusual is happening, eventually you, as a listener, come to accept it yourself.