In classical mythology, a prophetess in Troy during the Trojan War whose predictions, although true, were never believed by those around her. Apollo had given her the gift of prophecy but made it worthless after she refused his amorous advances. The Greeks captured Cassandra after their victory and sacrilegiously removed her from the temple of Athena. As a result, Athena helped cause shipwrecks and enormous loss of life to the Greeks on their return home.
Note: A “Cassandra” is someone who constantly predicts bad news.