Work Weirdness

Got more hours at work for the indefinite future. Supervising consumers as they go about their work day. Nothing i haven't done before, and not all that complicated. The weird thing is my Dad is there and I have to refer to him as Jeff. Now usually I don't hear his given name like that. If its not "Dad!" it's "Jeffery!" or "Jeffery Glenn!" usually because he's done something borderline creepy, or he's befouled an area of a house. I don't have a problem with it its just weird. Why is it that using his name instead of the title makes me pause in conversation? I've heard him get yelled at for a long time, from quite a few different people. Family and friends. How does "Jeff" differ from "Dad"? Could Dad be the part that played video games with me, and taught me how to play catch, and Jeff is a piece of him that I've only glimpsed? Who could this stranger be that has known me all my life?