Pocketbooks and Willys!

"Mama. Do girls have a hiney?" our son asked.
"Yes they do- we all do," I answered.
He seemed so confused. He headed back upstairs, then abruptly turned around.
"But I thought girls had a vagina?"
Dude almost fell to come out of the bedroom now.
"What is all this 'bout hineys and things?" he came in with volume.
He still can't be a big boy about calling body parts their names. He still refers to vaginas as pocket books and penis as privates or Willys. But I don't wanna free Willy!
I motioned with my hand for him (Dude) to bring the volume down.
"It's okay," I told him with a slight smile.
"Girls do have vaginas and boys have a penis," I told our son.
Dude was about to pass out. And he teaches Health!
"I have a penis?" our son asked.
"Yes. You use it every time you go pay your water bill," I giggled. "Every time you pee," I added.
Pointing to his penis, he said, "This is my hiney."
I now understood the confusion.
"No baby that is your penis and your bottom or butt is also called a hiney."
His sister came bopping down.
"I told you!" she laughed.
"Your sister is a female and she does not have a penis like you but she has a hiney."
He laughed so hard, then pointed to his sister.
"Mama called you a female!"
We have some work to do.