'Concubines' in the Bible

While under the influence of the wine, Belshazzar issued an order to bring in the gold and silver vessels -- the ones that Nebuchadnezzar his father had confiscated from the temple in Jerusalem -- so that the king and his nobles, together with his wives and his concubines, could drink from them.

So they brought the gold and silver vessels that had been confiscated from the temple, the house of God in Jerusalem, and the king and his nobles, together with his wives and concubines, drank from them.

Instead, you have exalted yourself against the Lord of heaven. You brought before you the vessels from his temple, and you and your nobles, together with your wives and concubines, drank wine from them. You praised the gods of silver, gold, bronze, iron, wood, and stone -- gods that cannot see or hear or comprehend! But you have not glorified the God who has in his control your very breath and all your ways!