Newly arrived party from Oop North: "We just come over th'ill".
Me: Which "thill" was that?
NAPFON: "Cadder Eye-driss"
Me: " It's pronounced 'Cadder ID-riss'. Where did you come from?"
NAPFOM: "Borth! Dornt gu t'Borth!"
Me: "I certainly won't. Where are you headed next?"
NAPFOM: "Muh KIN lith"
Me: "It's pronounced Muh CHIN lith"
NAPFON: "Oh. Right. Ta."
Me: "Don't mention it"

It occurs to me now, having written this down and read it over, that it is just possible that the NAPFON may have misunderstood that last line as a polite response to their thanks, rather than an earnest instruction not to speak the name "Mu CHIN Lith" aloud. Such misunderstandings have been irritatingly frequent in my life.