Oubliette

[Sarah]

A dungeon with an opening only at the top, found in some oldcastles and other strongholds, into which persons condemned toperpetual imprisonment, or to perish secretly, were thrust, or luredto fall.Sudden in the sun An oubliette winks. Where is he Gone. Mrs.Browning.

[Magaret]

A [place] you [put] someone to [forget] about them

[Marquetta]

Actually: An [underground] [chamber] with access only from the top . (18th [Century])

Modern Slang: Asshole

[Couch Potatoe]

A secret dungeon with access only through a trapdoor in its ceiling.