英语词源字典 - 在线词源网站

anus (n.)[anus 词源字典]: "inferior opening of the alimentary canal," 1650s, from Old French anus, from Latin anus "ring, anus," from PIE root *ano- "ring." So called for its shape; compare Greek daktylios "anus," literally "ring (for the finger)," from daktylos "finger."[anus etymology, anus origin, 英语词源]
agastric: "Lacking, or apparently lacking, a stomach or an alimentary canal; characterized by this", Early 19th cent.; earliest use found in Anti-Jacobin Review. From a- + gastric, probably after French agastrique.