Dark data is the inactive or unused information stored away and overlooked,...

https://www.deltabookmarks.win/dark-data-refers-to-the-55-of-stored-information-that-organizations-keep-but

Dark data is the inactive or unused information stored away and overlooked, making up about 60%-80% of most companies’ data. This hidden stash isn't just costing money—it creates risk and adds noise that can confuse AI projects