Butt. Yes you can say it without sniggering.
A butt is an obsolete unit of liquid measurement in Britain. A butt is 126 wine gallons. Wine gallons? yes it is a thing, and explains another of those bizarre American differences. The American gallon is based on the old wine gallon measurement.
It sometimes seems that what ever measurement standard the rest of the world choses, America has to be different. So an American gallon is different from an imperial gallon: another reason why American recipes can be difficult to follow successfully. (that and "stick of butter". What kind of a measurement unit is a stick? Tablespoons of butter for something that normally comes in solid form is bad enough! ...mini rant over) Anyway an American gallon is based on cubic inches (231 cubic inches) while an imperial gallon is rounded to 4.54 litres. This means that an American gallon at a nominal 3.785l is considerably less than an imperial gallon. One of the reasons for that the Americans stuck with the old gallon measure is that the British imperial system was not adopted until 1825, by which time America had ceased to be a colony.
Butt may be archaic as a measurement, but it lives on in the names of British pubs, as does tun. A tun is equivalent to two butts. So we have pubs such as The Three Tuns in Henley,
or the Half Butt in Essex
Oh, and for another blindingly obvious fact (that I only recently realised) a quart is a quarter of a gallon.
Tomorrow I am going to continue the theme with old wines and Shakespeare. Then on Saturday I am looking forward celebrating Christmas Eve with more recent vintage wine and Shakespeare,. But more of that anon.