This etymology does not parse the word as a compound but as a simple word. It is clearly a graphic etymology: Greek scholars used to think in terms of letters rather than sounds. That means that their manipulations start from the graphic shape of the word rather than its pronunciation. And in a graphic system using uncials, ΒΙΒΛΙΟΝ, the diminutive of biblos, is close to ΒΕΒΑΙΟΝ, the neuter of the adjective bebaios "firm, steady", hence "enduring, lasting", since Α and Λ have a similar shape and are indeed often mistaken in manuscripts. The next step, which remains implicit, is the change of [e] to [i] in the initial syllable, but this was not a problem and could be backed by well-known cases where an [i] reduplication (in the present stem) alternates with an [e] reduplication (in the perfect stem), for instance tithēmi / tethēka. From the semantic point of view, the etymology defines the book by what may be its main function: to be a lasting monument (scripta manent): as a matter of fact, this etymology is fitted for the derivative biblion "book" rather than for biblos which means primarily "papyrus"