Original Dune
This article or section refers to elements from Original Dune.
Hidden Rank is a term used by the Bene Gesserit Sisterhood to indicate that an individual's true rank within the Sisterhood could not be publicly identified.
A known Bene Gesserit of Hidden Rank was the Lady Anirul Corrino, wife of the Padishah Emperor Shaddam IV.
Behind the Scenes
Frank Herbert never expanded on why it was necessary for someone fro the Bene Gesserit Sisterhood was required to have their rank hidden. It was possible that the Hidden Rank was used when a person's standing within the Sisterhood was so high that it was necessary to keep it secret, especially if one was married to the Emperor.