Atbash: the reversed Hebrew alphabet and the hidden names in Jeremiah

In the book of the prophet Jeremiah a mysterious name appears: Sheshach. The king of Sheshach, we read, will drink last from the cup of divine wrath. No city of that name is known to ancient geography, and Jewish translators and commentators already understood that it was a device. Sheshach is Babel, that is Babylon, written by a procedure we now call Atbash, one of the oldest substitution ciphers on record.

The principle of reversal

Atbash rests on a simple idea: the Hebrew alphabet of twenty-two letters is folded back on itself. The first letter, aleph, is exchanged with the last, tav; the second, bet, with the second to last, shin; and so on to the middle. The very name of the system sums up the rule, since it is formed from these four letters: aleph, tav, bet, shin. The same procedure serves both to encipher and to decipher, because the exchange is reciprocal.

Applied to Babel, that is bet, bet, lamed, Atbash yields shin, shin, kaf: precisely Sheshach, since Hebrew is normally written with consonants only. There were also variants built on similar logic, such as Albam, which divides the alphabet into two halves and exchanges the letters of the first with those of the second. Together they form a small family of permutations that Jewish tradition preserved and commented on for centuries.

The passages in Jeremiah

The name Sheshach occurs twice, in Jeremiah 25:26 and 51:41. In the same chapter 51, in the first verse, appears the expression Lev Qamai, literally “the heart of those who rise against me”, which through Atbash becomes Kasdim, the name of the Chaldeans, the people who ruled Babylon. The Targum, the ancient Aramaic paraphrase of the Bible, renders these passages directly as Babylon and Chaldeans, a sign that their meaning had long been understood.

Why would a prophet hide the name of Babylon? Some interpreters have thought of political caution, at a time when Babylon was the dominant power. Others believe it is rather a literary and sapiential game, since the same text names Babylon openly in many other verses. More than a real military secret, biblical Atbash looks like a way of giving the name an enigmatic aura.

Atbash in the kabbalistic tradition

In later centuries permutations of the alphabet became a tool of Jewish mysticism. In medieval Kabbalah, alongside gematria, which assigns a numerical value to letters, there was temurah, the art of exchanging letters according to fixed schemes. Atbash was one of these schemes. For the kabbalists the aim was not to hide information from an enemy but to discover further meanings in the sacred text, considered already present in the letters themselves.

In the twentieth century Atbash returned to the centre of a famous hypothesis. The scholar Hugh Schonfield proposed that the name Baphomet, the idol the Templars were accused of worshipping, was a word enciphered with Atbash: transcribed into Hebrew letters and reversed, it would give Sophia, Greek for wisdom. It is a fascinating suggestion but lacks documentary confirmation, and should be treated as such.

By modern standards Atbash is an extremely weak cipher: whoever knows the rule reads everything, and there is only one rule. Yet its historical importance is great. It shows that the idea of replacing one letter with another was already practised in the ancient world in a religious setting, and that secret writing was born intertwined with reflection on the power of words and names.