'Concubines' in the Bible

Belshazzar hath said -- while tasting the wine -- to bring in the vessels of gold and of silver that Nebuchadnezzar his father had taken from the temple that is in Jerusalem, that drink with them may the king, and his great men, his wives, and his concubines.

Then they have brought in the vessels of gold that had been taken out of the temple of the house of God that is in Jerusalem, and drunk with them have the king and his great men, his wives and his concubines;

and against the Lord of the heavens thou hast lifted up thyself; and the vessels of His house they have brought in before thee, and thou, and thy great men, thy wives, and thy concubines, are drinking wine with them, and gods of silver, and of gold, of brass, of iron, of wood, and of stone, that are not seeing, nor hearing, nor knowing, thou hast praised: and the God in whose hand is thy breath, and all thy ways, Him thou hast not honoured.