The Collaborative International Dictionary of English v.0.48:

Hydage \Hyd"age\, n. (Law)
   A land tax. See Hidage.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hidage \Hid"age\, n. [From hide a quantity of land.] (O. Eng.
   Law.)
   A tax formerly paid to the kings of England for every hide of
   land. [Written also hydage.]
   [1913 Webster]