Sheshach

Sheshach is a name appearing twice in Jeremiah (25:26; 51:41) that is widely understood as a coded designation for Babylon, employing the atbash cipher — a simple substitution code in which the letters of the Hebrew alphabet are reversed (aleph = taw, beth = shin, etc.), so that the letters of Babel (Babylon) become the letters of Sheshach. The Revised Version and most modern translations note this equation explicitly.

In Jeremiah 25:26, after listing the nations that will drink the cup of God's wrath, the prophecy culminates: and the king of Sheshach shall drink after them — placing Babylon last and greatest among those destined for judgment. In Jeremiah 51:41, the fall of Babylon is lamented with the same term: How is Sheshach taken! and how is the praise of the whole earth surprised! The use of the cipher may have served as a measure of protection for the prophet or scribe, or it may be a literary device emphasizing the totality of Babylon's fall — even its name will be obscured and overcome.