Forest

Although the Anglo-Saxon kings had game preserves amongst the English woodland, it was not until William I, and the Domesday Book that the word forest entered the language.

The word was derived from Medieval Latin foresta, itself from Classical Latin foris meaning "outside" -- land, not ncessarily wooded, which lay beyond the boundaries of manors and settlement.
Mostly forest was wooded, but as a term it could also include pasture, woodland and even land under agriculture.
As a definitional term its main thrust was that forest land was subject to forest law.