'Concubines' in the Bible

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

but hast lifted up thyself against the Lord of the heavens; and they have brought the vessels of his house before thee, and thou and thy nobles, thy wives and thy concubines, have drunk wine in them; and thou hast praised the gods of silver and gold, of brass, iron, wood, and stone, which see not, nor hear, nor know; and the God in whose hand thy breath is, and whose are all thy ways, hast thou not glorified:

Then the king went to his palace, and passed the night fasting; neither were concubines brought before him; and his sleep fled from him.