Another thread reminded me of this: When I was a kid, and even into my early teens, I was secretly convinced that adults must have a secret language that one is taught at a certain age. I have no idea where I got this notion, except that it could be related to my strong verbal skills and an assumption that if I could grasp English easily from childhood, surely adults - whose minds were seemingly far more developed than my own - must have some kind of language to which they alone were privy.
It's even more probable that while I had a good grasp of the grammar and syntax of language, my autism gave way to an intuition that I was missing something in everyday speech. I could hear and understand the literal meaning of words, but I noticed discrepancies between the words spoken or written, and the apparent meaning that they conveyed to other people.
In restrospect, I should have known better given how poorly many adults manage using English in day-to-day communication, but the notion that my parents probably spoke a secret language away from kids was very real to me at the time.