An article from World Wide Words discusses the history of the word “forest,” which is more complicated than you might think:
The origin of the word forest is usually explained as coming from the late Latin phrase forestis silva, which was apparently applied to areas of land used by the Emperor Charlemagne for hunting. Here, silva meant “woodland” (as in “sylvan” and “silviculture”) and forestis meant “outdoor, outside” (apparently related to the Latin fores, “door”), so that forestis silva meant something like “beyond the main or central area of administration; outside the common law”. In time, the phrase became shortened to forest, but retained a sense of separateness and exclusion. It was this sense that the Normans brought with them when they invaded England in 1066. A forest for them and their successors was an area of unenclosed countryside, consisting of a highly variable mixture of woodland, heathland, scrub and agricultural land. Its purpose was to raise deer, which needed a variety of land—woodland to rest and hide in during the day, and more open land in which to feed at night….
By a process of transference, the meaning of the word forest gradually shifted, as the force of the old forest law declined after about 1500, from the legal area to the woodland within the forest, so giving us our modern sense of the word.
In between the two sections quoted above comes a discussion of forest law and what it entailed, and this should be read by anyone with a love for arcane and obsolete words: “The forests had an army of staff to look after them: seneschals, justiciars, regarders and verderers administered the forest laws…. The courts that heard offences were either courts of eyre (travelling courts to hear serious offences, from the Latin iterare, ‘to travel’, which also gives us words like ‘iteration’), or of swainmote (a court held three times a year principally to control the pasturage of pigs in the forest…)” And we get puture, assarts, agisters, fewmets, and “the ceremonial gralloching or evisceration of the deer after the kill.” Fun for one and all!