I recently re-read Dune for something like the 5th time. I love the book; I find that I always look at water in a different way for months after I’ve read it.
On reading it this time, I came across this word in the text and the glossary:
As a native French-speaker, I immediately saw what it must be: Écoutez! For the non-French-speakers among you, that translates to Listen!
I searched on Google for any other mentions of ikhut-eigh and écoutez or écouter, and found nothing. So I’m possibly the first one to have seen this connection. It wouldn’t be completely strange, either. There are several words in the glossary that have clear French roots: verite, proces verbal, and of course, melange, the spice itself. So I’m convinced that this little mystery is solved. Unless Frank Herbert completely made it up, of course.