noun
Refers specifically to the ancient Athenian practice of ostracism, where citizens voted to exile a person by writing names on pottery shards (ostraka). Not used for modern social exclusion.
古代アテネでは、貝殻追放によって政治家を追放することがあった。
In ancient Athens, politicians were sometimes exiled through ostracism.
追放 is a general term for banishment or expulsion, while 貝殻追放 specifically denotes the historical Athenian practice of ostracism.
From 貝殻 (seashell, here referring to pottery shards used as voting tokens) and 追放 (banishment). A calque of the English 'ostracism', which itself derives from Greek 'ostrakon' (pottery shard).