noun
Ansei Purge
A major political purge in the late Edo period (1858–1860) led by Ii Naosuke, targeting opponents of the shogunate's policies.
安政の大獄は、井伊直弼が反対派を弾圧した事件です。
The Ansei Purge was an incident in which Ii Naosuke suppressed his opponents.
Named after the Ansei era (安政) and the term 大獄 (great prison/purge). The exact derivation is straightforward from the historical context.