JonathanC, I'm sure you know that I am a real nurse, and you bring up a good question that actually made me stop and think for a few minutes. What do I say, and to whom do I say it too? I definitely change what I am saying depending on which gender and how old the person is that I am talking to. For example........
If the woman patient is 60ish or older I almost always call their vagina a vagina. If my patient is NOT uptight and younger I will often say girly parts. They know exactly what I mean and it actually puts them at ease and usually less embarrassed. And no matter what the age is, breasts are always called breasts.
The same actually applies to my male patients. If they are older, penis is called a penis, and a scrotum is a scrotum. If they are on the younger side I still usually call a scrotum, but sometimes will call them "the boys", but I always no matter what the age is, a penis is always a penis.
Now for both sexes and no matter what the age is if the person is uptight and that is their personality I will call their buttocks their bottom. But if they are uptight because they are nervous, or they are comfortable or relaxed, then I will call their bottoms something more slang, like backside, or tush, tushy, or once in a while fanny.
So my guess is he was trying to relate to you, make you feel more relaxed, or more comfortable. Another thing, as BigK mentioned, he was trying to communicate better with you, you would be surpirsed how many adults do not know the proper terms for their major body parts. We don't expect you to know the names of all your bones, muscles, tendons etc, but it would be very nice if everyone knew the proper terms for their body parts that are gender specific, lol.
A little story that relates. When I was working in the ER I had a guy come in, he looked fine, no outwardly signs of bleeding or anything broken etc. I asked him what he came in for and he said he had a problem with "stuff". I said, "okay, what stuff?" He said, "my stuff". I again said "okay, I get that it's your stuff, but what kind of stuff are you meaning?" This went on for a few more minutes until he was finally able to be open enough to point to his body part, which was his penis. He admitted to me later that he honestly didn't know what the medical term for his penis was and he out of respect for me didn't want to say the word dick. I told him I greatly appreciated that he didn't. Then I think my face got a little red, lol. Not really sure.
Mashie