In the past Wikiversities and Wikibooks lived together. Six years ago es.wikiversity was created and all the content hosted formerly on es.wikibooks was transwiki imported to there, and the local content replaced with a template that indicated the content was moved and where to find it
After an agreement on our local village pump that after six years ago we didn't need any of those pointers anymore nor the namespaces I deleted all the content, leaving empty those namespaces.
As such, to finish the process, please kindly remove from es.wikibooks the following namespaces:
-  Wikiversidad
-  Wikiversidad Discusión
Discussion on the URL field. I'm a bureaucrat at es.wikibooks.