My Name is Nancy

Her official name is Diane, but, for some reason , I keep on calling her Nancy.

Her middle name is Patricia. Patty, the nickname, sounds ok to me.

Sometimes large classes of students ask me how I can remember their names immediately. They tell me their names at the beginning of the lesson, I remember all of them, one by one. 
This happens when I find that their names "marry" with their faces.
If , in my mind, they do not, I do not remember their names as well.

Same with Diane: it always takes me a certain fatigue, and a few seconds, to call her with her own name, because, to me, she is Nancy. Patty, at least....

Strange cooking lesson.... isn't it?