There is a legend that the city of Cracow has been founded by Cracus (Krak or Krakus). I found a book stating that his original name was Latin Grak or Grachus, who "lived at the Vistula river under the Panonnia mountains":
Please note, however, that this book cannot be trusted (I found quite fantastic theories there, for example unificating the Vandals with the Slavs). Another interesting thing was that the Latin term Bohemia comes from the Slavic word "Boh" meaning God. In the contemporary Polish this word is Bóg (phon. boog).