'Concubines' in the Bible

Belshazzar, while he tasted the wine, commanded to bring the golden and silver vessels which Nebuchadnezzar his father had taken out of the temple which was in Jerusalem; that the king and his lords, his wives and his concubines, might drink from them.

Then they brought the golden vessels that were taken out of the temple of the house of God which was at Jerusalem; and the king and his lords, his wives and his concubines, drank from them.

but have lifted up yourself against the Lord of heaven; and they have brought the vessels of his house before you, and you and your lords, your wives and your concubines, have drunk wine from them; and you have praised the gods of silver and gold, of brass, iron, wood, and stone, which don't see, nor hear, nor know; and the God in whose hand your breath is, and whose are all your ways, you have not glorified.