'atbash' originates from Hebrew, specifically the sequence of Hebrew letters represented as 'אטבש' (Atbash), where the pairing of letters (for example Alef 'א' with Tav 'ת') reflects the cipher's mapping of first-to-last letters.

'atbash' entered modern English as a borrowing from Hebrew through scholarly and biblical studies in medieval and early modern Europe, retaining the original Hebrew form and meaning as it became used in descriptions of ancient cryptographic practices.

Initially it referred specifically to this method of letter pairing in Hebrew texts; over time the term came to denote the particular reversal substitution cipher more generally in studies of cryptography and linguistics.