'crypto-Jew' originates from Greek and English, specifically the Greek word 'kryptós' where 'krypt-' meant 'hidden', and the English word 'Jew' (from Latin 'Judaeus').

'crypto-' comes from Greek 'kryptós' which passed into New Latin/Modern English as the prefix 'crypto-'; 'Jew' developed from Hebrew 'Yehudi' → Latin 'Judaeus' → Old French/Middle English forms and became 'Jew' in modern English. The compound 'crypto-Jew' is a modern English formation combining these elements.

Initially it literally meant 'hidden Jew'; over time the term has retained that core sense but broadened to refer to anyone who conceals Jewish identity or practice (not limited to a single historical period).