Complex sentence: The title of "Turkish Slave" derives from the alleged presence of a turban, which is in fact a typical headwear of noblewomen of the time and which appears in numerous contemporary portraits.
Split into simpler sentences: The title of "Turkish Slave" derives from the misinterpretation of the sitter's headwear as a turban of a turban. It is in fact a typical headdress of noblewomen of the time, with examples appearing in numerous contemporary portraits.