jejunum

Ancient Greek and Roman physicians noticed something consistent when they opened a body: the middle section of the small intestine was almost always empty. The stomach held food, the duodenum held bile, the ileum held residue, but this middle stretch held nothing. They named it accordingly. Jejunum is the Latin adjective jejunus used as a noun, meaning fasting or empty.

Galen of Pergamon, writing in the 2nd century CE, documented the observation that cadavers consistently showed this section without contents. He attributed the emptiness to the gut's muscular action, which moved chyme through faster here than elsewhere. The Latin adjective jejunus had been used for centuries to describe hunger and fasting before anatomists applied it to this stretch of bowel.

Jejunus itself may connect to a Proto-Indo-European root meaning to be lacking or void. In classical Latin, the word described a person who had not eaten, a dry riverbed, and barren soil. Anatomical Latin borrowed it narrowly for this intestinal segment. By the 16th century, Vesalius listed jejunum intestinum in his systematic account of abdominal anatomy.

English adopted jejunum from Latin medical texts in the 17th century. The Oxford English Dictionary's earliest English citation dates to 1634. Today the jejunum is recognized as the primary site of nutrient absorption, handling iron, folate, and most vitamins. The name captures what early anatomists saw, not what modern physiology confirmed: a gut that looks empty is doing the most important work.