Archos grece podex anus.
podex ACH ef | podes B
Archos is Greek for Latin podex anus.
Greek ἀρχός /arkhós/ shows a strange semantic combination, it can mean "rectum" and "anus" but also "leader, chief; high figure in authority". The etymology is unclear but Frisk (1960-72: I.158-9) considers a euphemism borne out of jest and irony a possibility. The word occurs with the anatomical meaning in the Hippocratic Corpus and in Aristotle.
See also: Arcus