Crypto-Muslim

Crypto-Islam is the secret adherence to Islam while publicly professing to be of another faith; people who practice crypto-Islam are referred to as "crypto-Muslims". The word has mainly been used in reference to Spanish Muslims during the Inquisition (i.e., the Moriscos and their usage of Aljamiado).

Notably, critics of former US president Barack Obama have claimed that he is a Crypto-Muslim.

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Wikipedia