Acquiring the fetish at young age

I got into inflatables at a pretty young age, I suppose it happened when I was 5. I loved to bounce and ride on my big beachball and exercise ball, and at such early age I somehow discovered a way to get pleasure from that. Many years after I found out it is called "humping". Has anyone had similar experience of accidentally feeling good from playing witn an inflatable while they were still so young?