ullage—the space between the top of the liquid and the bottom of the cork in a bottle of wine.
This word traces to the Latin word for the bung-hole, which was oculus (metaphorically, an eye). The word passed into Old French as oeil, and from that came the verb ouiller (to fill up a barrel to the bung-hole). The ouillage was the remaining space. The word passed into Anglo-Norman, and then into English.
