Using proper words

I like the kids to know the proper names of their body parts, and Caleb was told by someone that his penis is a pee-pee. Well, I have been telling him that it is a penis, and using that term with him more lately. The subject came up tonight at the supper table. Caleb said, "We don't say pee-pee." I said, "That's right, we don't." Then, Nathaniel said, "Why do you say that anyway?" I said, "Say what?" Then he got kind of weird on me, and replied quietly, "Penis?" I said, "Well, because I want him to use the proper name, and I want you guys to use the real words." Then, Nathaniel told me it is just weird, and that it isn't a very nice word. So, I said, "Well, it would be like me calling you my So-so...or my S-S, instead of my son." He thought that was pretty funny, and that brought on some good laughs. So, I think he understands now.