My wife asked little David if he had enjoyed the trip.
"Yes it was great - we saw sheep, horses, goats, and f***ers."
Wife: "er, fine, fine. I know what the sheep and the rest are, but what is a f***er?"
David: "Oh, they're the animals that give us milk"
Wife: "but who said they were called, er, f***ers?"
David: "that was our teacher. Well actually she called them "effers," but we all knew what she meant."