Fun 4 is first of all a reference to the book's four collaborators. At the same time, the Chinese expression fang si (pronounced the same in Chinese as "Fun 4") can mean "unbridled," which describes the approach of the four authors in their quest to express different aesthetic viewpoints.
《放 4》主要是說放了四個設計家的作品，但又「放肆」地呈現不同的美學觀點。