Albert Barnes Commentary Jeremiah 13:18

"Say thou unto the king and to the queen-mother, Humble yourselves, sit down; for your headtires are come down, even the crown of your glory." — Jeremiah 13:18 (ASV)

The queen - that is, “the queen-mother;” the word literally signifies “the great lady.” The king’s mother took precedence over his wives.

Sit down - The usual position of slaves.

For your principalities ... - Rather, “for the ornaments of your heads, even the crown of your majesty, shall come down.”