The duodenum or ) is from Medieval Latin, short for intestīnum duodēnum digitōrum, which may be translated: intestine of twelve finger-widths (in length), from Latin duodēnum, genitive pl. of duodēnī, twelve each, from duodecim, twelve.American Heritage Dictionary, 4th edition The Latin phrase intestīnum duodēnum digitōrum is thought to be a loan-translation from the Greek word dodekadaktylon (δώδεκαδάκτυλοv), literally "twelve fingers long." The intestinal section was so called by Greek physician Herophilus (c.335–280 B.C.E.) for its length, about equal to the breadth of twelve fingers.online etymology: http://www.etymonline.com/index.php?term=duodenum}} is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine may be used instead of duodenum.