I’ve had many girlfriends say this to me before. I think it comes from being a man and having a perceived weakness in the form of a stutter. Not that stuttering is weakness, but it’s endearing to them for their “big strong man” to have a weak spot like that. This could also work swapping the genders as, if I ever had a girlfriend that stuttered, id find it endearing and would want to protect her from others that might not understand.