Dark data is the inactive or unused information sitting untouched in your...

https://www.golf-bookmarks.win/dark-data-is-the-55-of-stored-information-companies-don-t-use-but-still-pay-to

Dark data is the inactive or unused information sitting untouched in your systems—often making up 60%-80% of your stored files. It matters because it wastes space, drives up costs, and creates noise that can confuse AI projects