I also can't say the word 'initial' - it's something I struggle with at my job, too, because I have to have people initial certain documents. I always know when that word is coming up, so I am sure to take a deep breath before, and really calm by body. Sometimes it works, sometimes it doesn't, but it has helped me in the past to really let my body relax before I have to say that word. I have been guilty of just saying 'sign' instead of initial and hoping they 'correct' me and I can say "oops, that's what I meant!" and laugh it off.