What is an "incunable"?

WalksBySelf, I agree. I picked this up from Wiki: "The term incunabula was first used in the context of printing by the Dutch physician and humanist Hadrianus Junius (Adriaen de Jonghe, 1511–1575), in a passage in his work Batavia. "Junius set an end-date of 1500 to his era of incunabula, which remains the convention in modern bibliographical scholarship. This convenient but arbitrary end-date for identifying a printed book as an incunable does not reflect changes in the printing process, and many books printed for some years after 1500 are visually indistinguishable from incunables".

OK, but why is there a special name for books printed before 1501? The explanation should say