“this was after Jeconiah the king had departed from Jerusalem.” “Jeconiah” is also called “Jehoiachin” (2 Kings 24:8-9). The Babylonian deportation of Jeconiah along with the large numbers of people was in 597 BC. Jeremiah wrote this prophecy during the reign of Zedekiah, after the vast majority of the Judeans had been carried to Babylon, and much of the wealth of Jerusalem had been carried there too. The conquest of Judah began during the reign of Jehoiakim and lasted through the reigns of Jehoahaz and Jehoiachin. So Jeremiah’s letter came after most of the carrying away to Babylon had occurred but Jerusalem had not been destroyed yet, which happened in the eleventh year of Zedekiah (2 Kings 25:2).
“queen mother.” The Hebrew word translated “queen mother” is gebereth (#01404 גְּבֶרֶת), and in this context the “queen mother” is the mother of the king (BDB Hebrew-English lexicon). The queen mother was the most powerful woman in the kingdom, much more powerful than any of the wives of the king, who often did not have much real power at all. The mother of Jehoiachin was Nehushta, wife of Jehoiakim (2 Kings 24:8).