pun·cheon 2 
(pŭnchən)
(pŭnchən)n.
1. A cask with a capacity of from 72 to 120 gallons (273 to 454 liters).
2. The amount of liquid contained in a puncheon.
[Middle English punchoun, from Anglo-Norman ponchon, punching tool, cask (probably because the casks were inspected and marked with a punch); see PUNCHEON1.]