A unit of measurement

The hide was originally, in early Anglo-Saxon England (around the 7th century), an amount of land sufficient to support a family or household.

Later it became a notional unit of assessment, which served to quantify the contribution to public liabilities to be made by the owners or inhabitants of an area of land. These liabilities included the payment of a food-rent (known as feorm), the maintenance and repair of bridges and fortifications, the provision of a given number of soldiers to the fyrd and (later) the payment of a land tax known as geld, which was collected at a stated rate per hide.

In 1086, after the Norman Conquest of England, hidage assessments were recorded in Domesday Book and the Norman kings continued to use them (with amendments) for tax assessments until the end of the 12th century.

The hide was not a fixed area of land. It was a measure of value, not of area. The Anglo-Saxon word for a hide was hid (or its synonym hiwisc). Both words are believed to be derived from the same root hiwan, which meant “family”.

Wikipedia: Hide (unit)