Quintus can also be the latinized form of the relatively rare Etruscan male name Cuinte (also spelled as Cvinte), of which the meaning is unknown. See page 74 (or 260 - the page numbering is confusing) of the book "Mediterranean Studies: IV. Etruscan, V. Venetic" by George Hempl, which clearly states that Qvinte is an Etruscan name taken over into Latin and more or less latinized.http://books.google.nl/books?id=enyaAAAAIAAJ&pg=PA74&lpg=PA74&dq#v=onepage&q&f=falseHowever, some sources also state that Cuinte is the Etruscan(ized) form of Quintus. Since the Etruscans adopted many Latin names and the Romans in turn adopted many Etruscan names, I suppose both etymologies can exist next to one another at the same time.
http://books.google.nl/books?id=enyaAAAAIAAJ&pg=PA74&lpg=PA74&dq#v=onepage&q&f=false
However, some sources also state that Cuinte is the Etruscan(ized) form of Quintus. Since the Etruscans adopted many Latin names and the Romans in turn adopted many Etruscan names, I suppose both etymologies can exist next to one another at the same time.