rectum

The rectum takes its name from the idea of a “straight intestine.” English borrowed rectum from New Latin, where it was shortened from Latin rectum intestinum, literally “the straight intestine”; rectum is the neuter form of rectus, “straight.” The Latin anatomical phrase translated an Ancient Greek expression meaning “straight gut,” used in writings of the physician Galen. Galen described the rectum in animal corpses as straight, unlike the curved human organ, so the name reflects that observation rather than an accurate description of human anatomy. The English noun names the terminal part of the large intestine.