There is actually a unit of measurement for wine (or whiskey) casks called a "butt." That means if you fill the barrel up, you technically have a buttload of wine—though you'd probably just call it a full butt.
A butt is 108 Imperial gallons. It is also half a tun which is 216 gallons. A third of a tun, 72 gallons, is a puncheon, and a third of that is a tierce. Half of a butt, 54 gallons, is called a hogshead. A boring old barrel is just 36 gallons, and a kilderkin is 18 gallons. The smallest unit is nine gallons, and it's call a firkin. You can also call it a rundlet.