"Hidden storage" refers to a space or compartment that is not easily visible or noticeable, where you can safely keep things out of sight. Full definition
Fit owners can flip up the rear seat bottoms to reveal hidden storage compartment and to accommodate tall and skinny items like large framed pictures. (truecar.com)
For bathrooms that are a tight squeeze, consider a flip - down shelf with hidden storage behind it. (bhg.com)
They are great for hiding storage under the crib! (blog.guguguru.com)