So, DD has got quite a grown up name. She was born as a 5lb scrap and it didn't suit her so we kep calling her Bean as we had in utero.
18 months later she is still Bean.
I would quite like to start calling her by her real name but not sure how exactly without confusing the hell out of her. She responds to Bean, knows it's her name, can say it. She just about knows her real name is also her (she will point to herself if asked "who is X") but she can't say it and I suspect won't be able to for a while.
If your DC had a nn as a baby/small child, when and how did you start calling them by their real name?