Nergalsharezer - (Easton's Bible Dictionary)
Nergal, protect the king! (1.) One of the "princes of the king of Babylon who accompanied him in his last expedition against Jerusalem" (Jer. 39:3, 13).
(2.) Another of the "princes," who bore the title of "Rabmag." He was one of those who were sent to release Jeremiah from prison (Jer. 39:13) by "the captain of the guard." He was a Babylonian grandee of high rank. From profane history and the inscriptions, we are led to conclude that he was the Neriglissar who murdered Evil-merodach, the son of Nebuchadnezzar, and succeeded him on the throne of Babylon (B.C. 559-556). He was married to a daughter of Nebuchadnezzar. The ruins of a palace, the only one on the right bank of the Euphrates, bear inscriptions denoting that it was built by this king. He was succeeded by his son, a mere boy, who was murdered after a reign of some nine months by a conspiracy of the nobles, one of whom, Nabonadius, ascended the vacant throne, and reigned for a period of seventeen years (B.C. 555-538), at the close of which period Babylon was taken by Cyrus. Belshazzar, who comes into notice in connection with the taking of Babylon, was by some supposed to have been the same as Nabonadius, who was called Nebuchadnezzar's son (Dan. 5:11, 18, 22), because he had married his daughter. But it is known from the inscriptions that Nabonadius had a son called Belshazzar, who may have been his father's associate on the throne at the time of the fall of Babylon, and who therefore would be the grandson of Nebuchadnezzar. The Jews had only one word, usually rendered "father," to represent also such a relationship as that of "grandfather" or "great-grandfather."