A dungeon is a room or cell in which prisoners are held, especially underground. Dungeons are generally associated with medievalcastles, though their association with torture probably belongs more to the Renaissance period. An oubliette or bottle dungeon is a basement room which is accessible only from a hatch or hole in a high ceiling; however, the description of these basement rooms as "dungeons" stems from the romanticised castle studies of the 19th century. There is no evidence to indicate that prisoners were really lowered through the angstloch into the dungeon using a rope or rope ladder as these 19th century accounts suggest. Archaeological finds, by contrast, indicate the use of these basement spaces as store rooms.
The word dungeon comes from Frenchdonjon, which means "keep", the main tower of a castle. The first recorded instance of the word in English was near the beginning of the 14th century when it held the same meaning as donjon. The proper original meaning of "keep" is still in use for academics, although in popular culture it has been largely misused and come to mean a cell or "oubliette". Though it is uncertain, both dungeon and donjon are thought to derive from the Middle Latin word domimus, meaning "lord" or "master". In French, the term donjon still refers to a "keep", and the English term "dungeon" refers mostly to oubliette in French. Donjon is therefore a false friend to dungeon. An oubliette is a basement room which is accessible only from a hatch or hole in a high ceiling; however, the description of these basement rooms as "dungeons" stems from the romanticised castle studies of the 19th century. There is no evidence to indicate that prisoners were really lowered through the angstloch into the dungeon using a rope or rope ladder as these 19th century accounts suggest. Archaeological finds, by contrast, indicate the use of these basement spaces as store rooms. The use of "donjons" evolved over time, sometimes to include prison cells, which could explain why the meaning of "dungeon" in English evolved over time from being a prison within the tallest, most secure tower of the castle into meaning a cell, and by extension, in popular use, an oubliette or even a torture chamber. The earliest use of oubliette in French dates back to 1374, but its earliest adoption in English is Walter Scott's Ivanhoe in 1819: "The place was utterly dark—the oubliette, as I suppose, of their accursed convent."
Although many real dungeons are simply a single plain room with a heavy door or with access only from a hatchway or trapdoor in the floor of the room above, the use of dungeons for torture, along with their association to common human fears of being trapped underground, have made dungeons a powerful metaphor in a variety of contexts. Dungeons, as a whole, have become associated with underground complexes of cells and torture chambers. As a result, the number of true dungeons in castles is often exaggerated to interest tourists. Many chambers described as dungeons or oubliettes were in fact storerooms, water-cisterns or even latrines. An example of what might be popularly termed an "oubliette" is the particularly claustrophobic cell in the dungeon of Warwick Castle's Caesar's Tower, in central England. The access hatch consists of an iron grille. Even turning around would be nearly impossible in this tiny chamber. A "bottle dungeon" is sometimes simply another term for an oubliette. It has a narrow entrance at the top and sometimes the room below is even so narrow that it would be impossible to lie down but in other designs the actual cell is larger. The identification of dungeons and rooms used to hold prisoners is not always a straightforward task. Alnwick Castle and Cockermouth Castle, both near England's border with Scotland, had chambers in their gatehouses which have often been interpreted as oubliettes. However, this has been challenged. These underground rooms were built without latrines, and since the gatehouses at Alnwick and Cockermouth provided accommodation it is unlikely that the rooms would have been used to hold prisoners. An alternative explanation was proposed, suggesting that these were strong-rooms where valuables were stored.