Dark data is the unused or forgotten information stored in your systems, often...

https://wiki-canyon.win/index.php/Dark_Data_and_AI_Governance:_What_Should_Be_Blocked_from_Ingestion%3F

Dark data is the unused or forgotten information stored in your systems, often making up 55% of your data. It’s costly because it wastes storage and raises security risks. For AI projects, dark data adds noise, slowing down results