A matter of anatomy
Turns out they're not the only ones confused. In this selection the Prince and Princess are having a disagreement:
"...Do not upstage the queen of England. And," he said, raising his finger, "with a bosom, no less."
"Why do you say that, Freddy? Why do you talk that way?"
"Because," said Freddy, with the urgency of a hunstman who has got his fox in a barrel, "it is a fact in brilliance that you upstage the queen, the duke, me, my brother, my sister, the monarchy itself, indeed, the whole bloody country, with--what?--a bosom?"
"Yes, a bosom?"
"But Freddy, why do you say that? You know I've got two."
This shut Feddy up like a stun grenade. "Two what?" he finally said.
"No you don't, you've got one bosom. One, only pne."
"No I don't, I've got two," she said proudly, holding a hand up to cup one breast, and then another. "One here, and one here. Sit down, Freddy. Sit down there."
"Okay," Fredericka said, as if talking to an agitated hospital patient, "look at me."
"Now, Freddy," she said, pointing to her head, "how many heads do I have?"
"That's ridiculous!" Freddy protested.
"How many heads do I have, Freddy?"
"You have one head, Fredericka."
"Good. Now"--she lifed her blouse, exposing her navel--"how many boutons de la ferme do I have?"
"What are boutons de la ferme?"
"That's what the French call farm buttons."
"What are farm buttons?"
She pointed at her navel.
"Since when is that a farm button?"
"It's always been a farm button. The question is, how many do I have?"
"And how many hands?"
This went on for a while until Fredericka paused dramatically, smiling because Freddy, like a circus horse, had counted flawlessly in ones and twos. "Now," she asked, "tell me. How many bosoms do I have?"
"One," said Freddy.
"You're hopeless," she said. "I have two. You used to be quite fond of them."
"You have one, and I am quite fond of it."
"Freddy, look," she said tentatively, "just look. Two. Not one. Two. Two bosoms."
"Sorry, Fredericka, but the fact is, and I know it for sure, and would stake my life on it, that you have only one."
"The hell I do!"
"Yes. You've got one bosom, two teats (spelled t-e-a-t and pronounced tit), and two breasts. And that's a fact."
"Oh, So now I've got five!"
"No, you've got only one."