I see! I am no expert on this matter but from what I’ve heard from different experts is that the most common cause of stuttering is mild trauma which many people face at a very young age that’s why most of us won’t even remember how or when we started to stutter. One of the doctors that i met a few years ago said that children can get traumatised very easily as kids. Like being alone in the dark and scared for some time or being scolded by a parent is enough to trigger it. The good thing is that it can be fixed but that one need to thoroughly study his/her stuttering patterns and triggers to minimise the stutter.