Dark data is the inactive information companies hold but rarely use, making up...

https://www.bookmarkidea.win/dark-data-is-the-55-of-your-stored-information-that-s-never-accessed-or-used

Dark data is the inactive information companies hold but rarely use, making up 60-80% of all stored data. It matters because keeping this unused data costs money—around $2.5 million per year for some businesses—while adding little value