I'm currently in about the middle of God Emperor of Dune, and I have noticed something weird about the Ix. It says repeatedly that they don't know that IX is a reference to the fact that their home planet is ninth in the system, and their name is a debasement of the roman numeral for nine. It also states multiple times, in the voice of whatever character is noting this fact, that the Ixians seem unaware of it. Usually this is with a touch of derision.
My question is this: Since the Bene Gesserit are based on a world named Wallach IX, how did the Ix not make the connection? Is the name of the world pronounced 'Wallach nine" or "Wallach Ix"?
If the answer is a spoiler to a book I haven't read yet, kindly tell me and I'll drop the question to find out on my own. Likewise, if I've missed something glaringly obvious, please hit me with the dumbass stick.

Thanks!