Dark data is the inactive or unused information that piles up without being...

https://future-wiki.win/index.php/What_Is_KAPPA_Data_Services_and_Why_Is_It_Tied_to_Python%3F

Dark data is the inactive or unused information that piles up without being analyzed or managed. It can make up 55% of stored data, leading to wasted storage and backup costs, sometimes costing businesses millions annually