transom

In architecture, a transom is the term given to a transverse beam or bar in a frame, or to the crosspiece separating a door or the like from a window or fanlight above it. Transom is also the customary U.S. word used for a transom light, the window over this crosspiece.^[1] 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. "Vasistas" sounds similar to the German phrase "was ist das?" ("what is that?"); hence folk etymology ascribes its origin to a visiting German's reaction to seeing a transom during a trip to France.