What is your opinion on grandparents picking their name?

So my MIL desperately wants our baby to refer to her and my FIL as Lolli and Pop. I loathe this idea. I cannot stand the thought of referring to her as Lolli. It is just so dumb to me (obviously I feel strongly about this). I'm okay with the normal variations of grandma and grandpa, like meemaw and peepaw, mimi and papa. That sort of thing. Lolli is so dumb to me and I want to tell her that she can refer to herself that way, but i'm not. Until she picks a more realistic one, I will refer to her as grandma. Am I being mean and am I wrong?