This is a common misnomer propagated by the modern Saresii themselves. The term Celtest was and still is used to identify an ancient space-faring society.
The correct name is Seenian.
The term Celtest derives from the old Seenian word Celteese-eese-em meaning Cosmic Siblings together and was used to describe the Saresii / Seenian partnership.
The Celtest Depot could mean an old Seenian or Saresii depot. But in this context, it usually means the Seenian Inheritance . A gigantic planet-sized storage containing everything the Last Seenians were able to save.
See Seenian Inheritance for Details (Please be aware that most details are classified)