Transom Light

Transom light (fanlight) is the customary U.S. word for a window over a door, which may be fixed or capable of being opened for ventilation. In England, the transom above a door is usually referred to as a fanlight, and occasionally as an "overlight", or by the French word "vasistas". The word "fanlight" derives from the fan-like shape of early transoms, which became a traditional part of the Georgian style. The French term is phonetically similar to German phrase "was ist das?" ("what is that?"). Hence folk etymology ascribes its origin to German chambermaids in France.