John Gill Commentary Jeremiah 23:40

"and I will bring an everlasting reproach upon you, and a perpetual shame, which shall not be forgotten." — Jeremiah 23:40 (ASV)

And I will bring an everlasting reproach upon you
Which was a just retaliation for reproaching, vilifying, and bantering his word: they who had been honoured so much and so long as the people of God, and their city counted the glory of the earth; yet now both they and that should be the byword of the people, and had in the utmost contempt, and that for ever, or at least a long time, even for a series of ages; which has been their case ever since their destruction by the Romans, and still is; for this cannot be restrained to the short captivity of seventy years in Babylon; though this reproach began then, and they never recovered their former honour and glory;

and a perpetual shame, which shall not be forgotten
the same thing in different words, to heighten their disgrace, and confirm the perpetuity of it.