This is the 6729th most frequent Dutch word.
wolff
"Wolff" is a surname in Dutch and not a standard dictionary word.
Here, 'Wolff' is used as a surname referring to a specific family.
De familie Wolff woont in een groot huis nabij het park.
The Wolff family lives in a large house near the park.
In this sentence, 'Wolff' refers to the proper name of a wolf featured in the book.
Hij las een boek over de wolf, genaamd Wolff in de bibliotheek.
He read a book about the wolf named Wolff in the library.
Here, 'Wolff' is treated as the surname of a notable individual in history.