My dad stuttered when he was a kid. In college I found out why. My dad was left handed originally. My grandma didn’t want him to be left handed. So she forced him to use his right hand. He did, when he did this he developed a stutter. Eventually he “became right handed” and eventually his stutter disappeared. Apparently that’s a thing. If you force somebody to use their other hand not their strong hand it can cause a stutter to develop.