So I get the "Papa," but why pink? Did he wear a pink t-shirt like Vegeta on the day he became infamous and she called him Pink Papa within earshot of everyone?
Regardless, the fact that he allows it considering it seems to be an insult in his own world means he warmed up to it through her.
Now, I'm starting to think it means Mother Hen or a feminine parent, which is not the first time I'm seeing this, which is funny.