When you are a maiden, you have a name of your own. It may have your paternal name with it, but it is a distinct name, and it is yours. People will call you by that name.
Babies do not automatically call their parents mother, father, mummy, daddy. You have to teach them. You may have to teach them by naming yourself as mummy in front of them. It is easier for the child to learn that you are mummy if they do not hear other adults calling you by your name. Your maiden name. And so you may start calling the father of your child ‘daddy’ and he may call you ‘mummy’ and to other adults in your life you may also be ‘mummy’ for the benefit of your child. I didn’t go this way, but I’ve seen it done.
Granny is not a life change that results from your own action in the way that becoming mummy does. Being granny may mean that the people who once called you mummy are now calling you granny so that their children learn to call you granny. Other adults in your life may choose to reinforce this. You may find yourself calling our own offspring mum and dad for the benefit of the grandchild.
Of course there’s a similar pattern for men. However, men have traditionally had roles and identities outside the household. People to call them by their names and treat them as distinct individuals. Inside the house, trapped in the domestic sphere, there is a lot less room to be anyone other than mother or grandmother. Not a specific, named identity. Not a distinct person. A title. A job description. A loss of personal identity into the ocean of mothers and grandmothers.
Names have power. I wonder how many of our female ancestors lost their sense of personal identity to the titles given them.