The Swedish historian Johann Erich Thunmann (1746–1778), professor at the Halle University, was the first to manifest interest to the origins of the East European peoples. In his Untersuchungen über die Geschichte der östlichen europäischen Völker, he claimed a Cuman origin of the Bessaraba dynasty of Walachia as well as of the lords of Carbona (Southern Dobroudja), statements supported even nowadays by scholars like O. Pritsak and I. Vasary. This paper proves that Thunmann’s assertions are based on the Polish chronicles concerning the events of the mid-thirteenth century and on the Greek memoirs of John Kantakouzenos. Bessarabia, the country between the rivers Prut and Dniester and the Black Sea, was not the fatherland of the Bessaraba dynasty of Wallachia, but a province conquered by the Romanians on the Mongols in the last third of the 14th century.