A heated room in a monastery or other communal building where people could warm themselves, especially during cold weather.
From Latin calefactorium (warming place), from calefacere (to make hot) plus the place suffix -orium. Common in medieval monastic architecture.
Monasteries had almost no other heated spaces besides the calefactory—monks copied manuscripts with frozen fingers in their cells, making the rare hours by the warming-room fire absolutely luxurious by comparison!
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