What is the origin of freebooter?

Freebooter may appear to be an English-language compound, but in fact, it’s Anglicized from the Dutch term vrijbuiter, a combination of vrij “free” and buit “booty”—a compound word about treasure that is well suited for a pirate-related term. Buit and its English cognate booty derive from a Germanic source meaning “exchange” or “sharing of the spoils.” Freebooter has one other relative in English, and an unexpected one: filibuster, in the historical sense of “unauthorized military adventurer.” While freebooter is a direct borrowing from Dutch, plus a spelling change, filibuster is a borrowing of Spanish filibustero, one of several words meaning “pirate,” via French from the same Dutch term, vrijbuiter. Freebooter entered English in the late 1500s.