Bigthan in the Bible Encyclopedia - ISBE

big'-than big-tha'-na (bighethan, bighethana'; Septuagint omits name): One of the two chamberlains or eunuchs of Xerxes ("Ahasuerus") who conspired against the king's life, the conspiracy being detected by Mordecai and the culprits hanged (Est 2:21). Possibly these men had been partially superseded by the degradation of Vashti and were thus prompted to take revenge on Xerxes.