This is purely psychological. You can't say the word did specifically because you're have a huge amount of fear for the word. Start saying it (with stuttering, yes) and then give it two weeks and you'll be fine over it. Then another word comes along, and the process continues... It's the same with saying your own name for many stutterers. You stutter on your own name because you're afraid of stuttering on it. This is an especially common fear because of the social stigma of first impressions. Stuttering here is the worst place. Confidence and giving zero fucks is the remedy.