duodenum (n.)

"first portion of the small intestine," late 14c., also duodene, from Medieval Latin duodenum digitorium "space of twelve digits," from Latin duodeni "twelve each" (from duodecim "twelve;" see dozen). Coined by Gerard of Cremona (d. 1187) in "Canon Avicennae," a loan-translation of Greek dodekadaktylon, literally "twelve fingers long." The intestine part was so called by Greek physician Herophilus (c. 353-280 B.C.E.) for its length, which is about equal to the breadth of twelve fingers. The classical plural is duodena.