The Holding Tank (aka Fish Bowl, if the Tank is made up of mostly see through material). is quite different that from The (Drunk Tank). The Holding Tank is where every single "new" inmate waits while getting processed in to whatever jail or prison they will be living at.

The Holding Tank is a staging area for all inmates waiting for their Court hearing, (usually in big cells with one or more toilets).

A holding tank is a common euphemism that is used ambiguously throughout the jail/prison community. There are many times and many reasons that an inmate might be placed in a Holding Tank. i.e. in process, waiting for court, waiting to bail out, out process, and so on.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.