The people called it "theorbo", but the scholar having identified it with the instrument of classic Greece and Rome called it barbiton. The barbiton had nine pairs of gut strings, each pair being in unison. Dictionaries of the 18th century support Fludd's use of the name "barbiton". G. B. Doni mentions the barbiton, defining it in his index as "Barbitos seu major chelys italice tiorba", and deriving it from lyre and cithara in common with testudines, tiorbas and all tortoiseshell instruments. Claude Perrault, writing in the 18th century, states that "les modernes appellent notre luth barbiton" (the moderns call our lute barbiton). Constantijn Huygens declares that he learnt to play the barbiton in a few weeks, but took two years to learn the cittern.