Pomaks were converted to Islam during the period of Ottoman Empire. But, as was the case for other Bulgarians and Greeks, they must have been Christians before Ottoman Empire conquered Southeastern Europe.
They speak a dialect of the Bulgarian language which contains many Turkish and Greek borrowings. Even the grammar and syntaxis of Pomak has been influenced by those two languages. It has not a standard written form, and Arabic, Cyrillic, Latin or Greek alphabets have occasionally been used for writing Pomak. Ancient Thraces probably spoke a language closely related to Lithuanian and Latvian; since these languages are closely related to Slavic tongues, one can easily explain the fact that almost all people living where ancient Thrace used to live speak a Slavic language.
Now Pomaks carry a semi-nomadic, agricultural or pastoral life, and study in Turkish schools in Xanthe and Komotini. Turks consider Pomaks, as well as other Moslem populations of Greece, to be of Turkish origin. This is true of the majority of Moslem populations in Greece, but that seems not to be the case as regards Pomaks.