It is said that the pancreas was described first by Herophilus of Chalcedon in about 300 BC, and the organ was named by Rufus of Ephesus in about 100 AD. However, it is an established fact that the word pancreas had been used by Aristotle (384-322 BC) before Herophilus. In Aristotle's Historia Animalium, there is a line saying "another to the so-called pancreas." It is considered that the words "so-called pancreas" imply that the word pancreas had been popular at the time of Aristotle, but it had not been authorized yet as an anatomical term. However, the word pancreas presumably has been accepted as an anatomical term since Herophilus.