Know why cattywampus was trending last week?
"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; cf. Greek daktylios "anus," literally "ring (for the finger)," from daktylos "finger."
anus a·nus (ā'nəs)
n. pl. a·nus·es
The opening at the lower end of the alimentary canal through which solid waste is eliminated from the body. Also called anal orifice, fundament.
The opening through which feces pass out of the body.