Pliny, Natural History 36.131, records lapis Assius, the stone of Assos, as flesh-consuming, and the adjective sarkophagos transferred from the stone to the coffin made of it. Greek inscriptions use sarkophagos for coffins. Modern Egyptology and archaeology retain the word for stone coffins generally, regardless of any flesh-eating property.
The Assos limestone story became a quiet legend of its own: a stone so hungry it ate the dead in forty days. Repeaters rarely note that quick decomposition has many mundane helpers, heat, moisture, chemistry, and that no controlled test of the famed stone survives from antiquity.
The darker observation: every language hides embalmer's candor in its coffin words. English says sarcophagus with a straight face in gift shops. The euphemism succeeded by becoming unpronounceable to its own speakers.
We carved our fear of decay into the vocabulary of burial and then polished it into museum language. What other everyday words are still chewing?