Ulliage

Part of speech: noun, verb

Definitions

1. The amount by which a cask, bottle or tank falls short of being full, especially the empty space left at the top
2. The gap left between the liquid in a container and its brim, which is often measured to show how much has leaked or evaporated
3. The shortfall in a vessel's contents, typically the empty portion above the liquid that results from evaporation or leakage

Etymology: "Ullage" comes from Old French "ouillage," a term tied to filling casks. The root is "ouiller," meaning to fill up a cask, derived from "oeil" (eye), so the idea is of the cask's bung-hole or bunghole level being brought up to the eye. Put plainly, filling a barrel "to the eye" meant topping it up until liquid reached the opening, and the shortfall below that point was the ullage. English borrowed the word from that French source, and it stayed close to its cooperage origins. Its meaning is still concrete: the empty space left in a cask, bottle, or tank once liquid has evaporated, leaked, or been drawn off. Ships' logs and customs records used it to measure how much cargo had been lost in transit. The verb sense, to top up a container or to reduce its contents through leakage, follows the same practical logic as the noun, describing the act of filling or losing that gap.

Synonyms: shortfall, deficit, deficiency, leakage