Input (grade 13): Louvers originated in the Middle Ages as lantern-like constructions in wood that were fitted on top of roof holes in large kitchens to allow ventilation while keeping out rain and snow.
Output (grade 6): Louvers come from the Middle Ages as lantern-like constructions in wood that were fitted on top of roof holes. They were put in large kitchens to allow ventilation while keeping out rain and snow.