So now, I'm wondering about the etymology of "hogshead."

FWIW Department: Webster's says that hogsheads are "any of various units of volume or capacity ranging from 63 to 140 gallons, ... esp. a unit of capacity used in liquid measure in the United States, equal to 63 gallons." And a source previously cited by tsuwm mentions 100-gallon hogsheads. http://wordsmith.org/board/showthreaded.pl?Cat=&Board=miscellany&Number=26394 By those standards, the aforementioned 54-gallon hogsheads seem to be more like pigletpates.