For me this actually happened in two parts. The second of which is an experience that happened on here when I first joined.
As those who know me are aware, I enjoy both tickling, and women's feet.
My foot fetish started at my age of reason. I didn't fully realize I had a tickling fetish until I started writing to a straight male pen pal who also had a tickling fetish, when I was in my 20s.
When I was younger, I used to ask every female babysitter I had to smell their feet. Most thought I was a silly kid, so they said yes.
At one point, I asked a beautiful airline stewardess friend of my mom's to smell her feet. The lady said yes, and then told my mom. I was about.. eight at the time. I can remember my mom saying to me. "It really isn't right for you to ask my friend to smell her feet. don't do that".
I joined the TMF in 2002 after the passing of my straight male pen pal who was into tickling.
Shortly after I joined, I was on here one day, and someone who said they were a "Cop". said I was in trouble for supposedly talking to an underage girl. (It turned out this was false, as it was a troll who was causing trouble).
At that point, I said to my mom. "I think I have a problem, I joined this site about tickling, and someone who said they were a cop, said I'm in trouble. "
It turned out that I later found out from a very reliable source, that this was not true.
Thus, through certain.. experiences, my mom found out.
She just knew those incidents happened, but we never really discussed it.