louver

Etymology

Inherited from Middle English lover, from Old French lovier, lover, from Medieval Latin *lōdārium (attested as lōvārium), extension of lōdium, of unclear origin.

noun

1. A type of turret on the roof of certain medieval buildings designed to allow ventilation or the admission of light.
2. (chiefly in the plural) A series of sloping overlapping slats or boards which admit air and light but exclude rain etc.
3. Any of a system of slits, as in the hood of an automobile, for ventilation.