I'm finding this a very interesting thread. Thanks for asking the question, Olivia.
My T and I sometimes use each other's names in session. (We call each other by our first names.) But since it is just us two in the room, there isn't too much need. I think he uses my name for emphasis, when he really wants my attention and wants me to focus on something of importance he is about to say. I only use his name in the same situation, when I want him to really attend to what I am saying. I really like it when he speaks my name.
He also sometimes uses terms of endearment with me. It is rare, but occasionally they slip out, and they warm my heart.
Pinksoil, that's so interesting you remember the exact one time you spoke your T's name. Sounds like a significant moment to me! Maybe try it again...