transom
noun /ˈtrænsəm/
  /ˈtrænsəm/
- a bar of wood or stone across the top of a door or window
 - (North American English) (also fanlight British and North American English)a small window above a door or another window
 
Word Originlate Middle English (earlier as traversayn): from Old French traversin, from the verb traverser ‘to cross’.