The stopper used to seal a wine bottle is called a cork, while the one used to seal a wine-cask is called a bung. The word appeared in English in the mid fifteenth century and within a hundred years had inspired a variety of other words associated with the bung: for example, the opening into which the bung was stuffed became known as the bung-hole, the utensil used to cut the bung became known as the bung-knife, and thieves who pulled wallets from pockets—like bungs from barrels—came to be known as bung-nippers. Later on, in the mid eighteenth century, bung also came to mean tavern keeper, the person responsible for removing the bung from the wine cask. (The older name for this person—tapster, the person who controlled the tap—dates back to the eleventh century; the American equivalent, bartender, dates only to the early nineteenth century.) The word bung probably derives from the Latin word puncta, meaning pin-prick, which came to mean hole and then, by extension, material used to plug a hole.
A stopper or diaphragm that covers a vial and prevents fluids from escaping.