Donmeh

The Dönmeh (Turkish: Dönme) were a group of crypto-Jews in the Ottoman Empire who converted publicly to Islam, but were said to have retained their beliefs. The movement was centred in Salonica. The group originated during and soon after the era of Sabbatai Zevi, a 17th-century Jewish kabbalist who claimed to be the Messiah and eventually converted to Islam in order to escape punishment by the Sultan Mehmed IV. After Zevi's conversion, a number of Jews followed him into Islam and became the Dönmeh. Since the 20th century, assimilated Dönmeh might have intermarried with other groups and most have assimilated into Turkish society.

The Turkish word dönme is from the verbal root dön- that means 'to turn', i.e., "to convert", but in a pejorative sense. They are also called Selânikli "person from Thessaloniki" or avdetî "religious convert" (Arabic: عودة‎‎ ‘awdah 'return'). Members of the group refer to themselves simply as "the Believers" in Hebrew (Hebrew: המאמינים‎‎ ha-Ma'aminim), or "sazanikos," Turkish for "carp" in honor of the changing outward nature of the fish. An alternate explanation of this self-nomenclature is the prophecy that Sabbatai Zevi would deliver the Jews under the sign of the fish.

Despite their conversion to Islam, the Sabbateans secretly remained close to Judaism and continued to practice Jewish rituals covertly. They recognized Sabbatai Zevi (1626–1676) as the Jewish Messiah, observed certain commandments with similarities to those in Judaism, and prayed in Hebrew and later in Ladino. They also observed rituals celebrating important events in Zevi's life and interpreted Zevi's conversion in a Kabbalistic way.

...
Wikipedia