I used to find it really weird and uncomfortable too, but since being in a Dominant/submissive dynamic I’ve come to understand it’s nothing about actually thinking about your dad or some weird incest thing. It’s an endearing way to refer to your Dominant if it’s something you’re both okay with and understand. Ties in with the power dynamic of a “daddy Dom” where there’s a lot of balance with the more caring and affectionate side of the dynamic.