I refer to my father as “Daddy” but I use it as if it was his name, when talking to him or talking about him to friends. I would say"Hey Daddy, where are you going?" if talking to him, or “Daddy needs more chemo” if talking to close friends. I never say “my Daddy.”
My maternal grandmother is called “Nanny” by pretty much everyone. A large amount of her mail is addresses that way.
My Mom is “Momma” in the same vein as my Dad is “Daddy”
Well, depends what you consider fun. To me using babytalk and calling my girlfriend stupid pet names routinely is just stupid, not fun. Note that I say “routinely”. I will use any number of pet nicknames ocassionally to underline my expression of affection, or jokingly but I think it is utterly stupid for adults who are communicating matter-of-factly to be using baby talk and pet names continually. They should be reserved for emphasis but is you use them all the time they lose any significance. People like this deserve a shot in the head. And that is being kind.
I have always called my father Daddy and it just never occurred to me to stop. That’s his name. I’m from Northern Virginia, near DC. Not a yankee, but hardly the Deep South. My Father is from New Hampshire, and has never objected.
On one occasion, a guy I worked with did sorta sneer at me about it, but then he was a just a snarky miserable sort anyway. He was from Michigan, and one of those types who have always assuaged their own insecurities by dismissing the Intelligence level of the citizens of the Southern US. Funny how he had to move down here to find employment . . .
I find the tone of the OP to be a bit sneering as well, come to think of it.
I am 35. Once, when I was about 12, I referred to my Dad as “Daddy,” in front of a friend, my Mom, and my friends’ parents. I was mortified. I never before or since, as far as I can recall, have referred to him as “Daddy.”
So this isn’t more common in the South than it is everywhere else, is it? These answers seem to be scattered. If anybody cares, I’m an adult from So. California, and I still call the old man “Daddy.”