A deaf old lady walks into her local fishmongers and asks for a piece of cod
"Sorry, Ma'am, we've got no cod"
"Yes, sonny, a nice piece of cod"
"We have NO cod"
"I don't want haddock, just the cod"
This exchange continues with the fishmonger getting more and more exasperated. He grabs a piece of paper and in big bold letters writes CFOD and shows it to the lady. With a puzzled look, she says
"There's no f in cod"
"That's what I've been trying to tell you!"