What is Arrent?

Legal Definition
In old English law. To let or demise at a fixed rent. Particularly used with reference to the public domain or crown lands; as where a license was granted to encose land in a forest with a low hedge and a ditch, under a yearly rent or where an encroachment, originally a purpresture, was allowed to remain on the fixing and payment of a suitable compensation to the public for its maintenance.
-- Black's Law Dictionary