I know it comes from like a shock of a certain fact or activity. I stutter from the news that my parents divorced when i was 6 yo I immediately started stuttering, I connect it with that I loved my family and was always with them and the fact that i wasnt going to love with my big brother shocked me the most. Also I have a friend that stutters from a friend pushing him into a pool again when he was around 5-7 yo. I think you get the idea where the stutter comes from, the younger the bad thing (the shock) happens more likely it is to stutter