How chose your nickname?

 :)

A child of 6 years old: My father knows everything.
Of 15 years old: I also know as many things as my father…
Of 20 years old: My father doesn’t know anything…
Of 30 years old: And my father knows some things…
Of 40 years old: It won’t be wrong if I get the opinion of my father…
Of 60 years old: How many things my father had known. Only if he was alive to get his
Opinion