What is the meaning of ὄστρακον?

earthen vessel

  1. fragment of such a vessel, potsherd
  2. earthen castanet

fragment of such a vessel, potsherd

earthen castanet

the hard shell of animals such as mollusks and turtles

  1. mother of pearl
  2. eggshell

mother of pearl

eggshell

Source: wiktionary.org