Something about this word that you can roll around the mouth like a good swig of wine or cognac, the removal of which would result in its ullage in the barrel or bottle.
The Oxford English Dictionary says it refers to the ‘amount of wine or other liquor by which a cask or bottle falls short of being quite full (originally the quantity required to make good the loss by leakage or absorption)’, and by extension any loss of liquid whether by evaporation or leakage. It can also mean liquid that has oozed through something, or the metal wasted in engraving, or the amount a container is short of being full.
Intriguing use by Mervyn Peake, referring to an ‘ullage of sunflower’.
It comes from the Anglo-Norman French ulliage, from Old French euillier ‘to fill up’, originating in the Latin oculus (‘eye’, referring to a container’s bunghole).
A round old word. See if you can slip it in to your next conversation over a fine malt whisky.
Source: Oxford English Dictionary online