Sheshach appears in Jeremiah as a coded reference to Babylon, employing the Atbash cipher where letters are reversed (first for last, second for second-to-last, etc.). In this system, Babel (בבל) becomes Sheshach (ששך). Jeremiah 25:26 and 51:41 both use this cryptogram, possibly for literary effect, rhetorical indirection, or symbolic purposes. Ancient Jewish and later interpreters recognized the cipher. The Septuagint sometimes transliterates it, other times renders it as 'Babylon,' showing early awareness of the equivalence.