What experience made you realize that tickling was sexual for you?

For me I was early puberty. I was always fascinated with feet and tickling but never understood it. A female childhood friend had stayed over and while we were supposed to be sleeping I was laying on the floor and she on my bed. I was probably 12. She let me tickle her foot and I tickled harder and harder and she would laugh and I remember her saying not my toes and that was the moment I knew. Lol