I used to ponder this question myself. But now I put the question to you! When did you first realise that you were a polyglot?
For myself, I realised when I moved to Italy and I was introduced at a party as someone who could speak English, Spanish, and French. Everyone wanted me to demonstrate my language abilities. So there I was, in front of 15 - 20 strangers, being asked to translate into the aforementioned languages what was being asked of me in Italian. I guess you could say it was one of my proudest moments so date