ostracism: [16] In ancient Greece, when it was proposed that a particular person should be sent into exile for a period, because he was becoming a danger to the state, a democratic vote was taken on the matter. The method of registering one’s vote was to inscribe the name of the prospective banishee on a piece of broken pottery. The pieces were counted, and if enough votes were cast against him away he would go for ten years.
The fragment of pottery was called an óstrakon, a word related to Greek ostéon ‘bone’ (source of the English prefix osteo-) and óstreon ‘oyster’ (source of English oyster). To cast such a vote was therefore ostrakízein (whence English ostracize [17]), and the abstract now derived from this was ostrakismós, source of English ostracism. [ostracism etymology, ostracism origin, 英语词源]