What is Butlerage?

Legal Definition
A butlerage was a duty of two shillings on every ton of wine imported into England by merchant strangers; so called because it was paid to the king's butler for the king. The tax was first implemented in 1302 and stopped being levied in 1809.
-- Wikipedia
Legal Definition
A privilege formerly allowed to the king's butler, to take a certain part of every cask of wine imported by an alien.
-- Black's Law Dictionary
Legal Definition
An hereditary crown duty of two tons of wine from every ship importing twenty tons or more. See 1 Bl. Comm. 315.
-- Ballentine's Law Dictionary