Crypto-Judaism

Crypto-Judaism is the secret adherence to Judaism while publicly professing to be of another faith; practitioners are referred to as "crypto-Jews".

The term is especially applied historically to Spanish Jews who outwardly professed Catholicism, also known as Conversos, Marranos, or the Anusim. The phenomenon is especially associated with Renaissance Spain, following the Massacre of 1391 and the expulsion of the Jews in 1492