My sister used to beieve that when you become a "grown up" you change your name to an adult name. This was because adult names were like Helen or Richard and kid names were like Daniel and Nicole.
A childhood belief about names

others believed things like this
- When I was a child, I thought that grown-ups were adult.— Gloria
- At the age of around five, I realized that my mum's and dad's names were not mum and dad!— yelloworpurple
- I used to believe my parents names were mom and dad till i was 9— Sophiae
- As my parents had given me a name, I thought that it was up to me to give them names tooAnon
- When I was very young, I believed that my parents actual names were "mum" and "dad". — Margo
- I used to believe that India and Indonesia were right next to each other since their names sounded alikeAnon