An octrooi is a patent. Historically, octrooien were not just required to protect inventions, but also to enter into certain types of businesses, similar to what we’d call a permit today. An octrooi could also grant permission to publish a book in a certain area.
Octrooien can often be found in the records of the landlords or the government. They typically describe the type of permission that is granted and name the patentee.

Patent for a mill, 1589. Collection Nationaal Archief (public domain)