A casemate, sometimes erroneously rendered casement, is a fortified gun emplacement or armored structure from which guns are fired. Originally, the term referred to a vaulted chamber in a fortress. In armoured fighting vehicles that do not have a turret for the main gun, the structure that accommodates the gun is termed the casemate. The word comes from the Italian casamatta, the etymology of which is uncertain. Some think that casamatta comes from casa, Italian for house and matto, Italian for mad but in this case meaning fake; casamatta seems to have been a common nickname given to a medieval siege machine called gatta, which had the appearance of a house. Others (Devic) think that it comes from the Arabic word kasaba, transliterated to kasbah, the word that originated the Spanish word for fortress: alcazaba. Menagio speculated that it came from the Greek word for pit, khasma, the plural of which is khasmata. Hensleigh Wedgwood thought that it came from the Spanish casa and matar, making a casemate a house in which killing happens. Others take matto in its archaic Italian meaning of dark, equivalent to the English matt, as in opaque, making a casamatta a dark house. Casematte were also used as military prisons, making use of their lack of light to add to the punishment. This explanation seems to be the most agreed upon.