`liberty` Of Furness. What Does It Mean?

[Sellergarth]

With regard to the following, could anyone please tell me what the word `liberty` means or refers to.
"From 1537, the lordship of Furness was held by the Crown, and was granted to the Duke of Albermarle in around 1666. It seems that the notion of a ‘Liberty of Furness’, with ‘Liberty’ courts, gathered momentum in the eighteenth century. The Liberty of Furness and a number of member manors eventually descended to the Dukes of Buccleuch, and to the Dukes of Dalkeith, who continued to hold courts for the Liberty and its associated manors into the early twentieth century".
Thank you

[Jonathan-Joe]

Chambers English Dictionary includes "the bounds within which certain privileges are enjoyed" in its definition of "Liberty". So, an area not controlled by the local government. Wikipedia - http://en.wikipedia.org/wiki/Liberty_(division)