A word can be difficult to pronounce and somebody could stutter on that sound, no matter what the beliefs are, yes. Now, the conception of that word with fear leads to more tension, more self-consciousness which can lead to the stuttering itself. In my case, the reason sometimes I stutter is anxiety. And it's funny, because I only stutter when I'm anticipating and paying attention to that "feared word". If I'm talking and my attention is put somewhere else, I say that " feared word" perfectly and without even noticing. Sometimes our brains likes to play tricks on us.