Καλή σφαιρική παρουσίαση της ιταλικής προέλευσης του τσαρλατάνου υπάρχει στον Ayto (Dictionary of Word Origins), που συνδυάζει αυτά που διαβάζω στο OED και στο Ετυμολογικό του Κέντρου:
charlatan
Charlatan is of Italian origin. It comes from the verb cialare ‘chatter, prattle’. Its original application was to the patter of salesmen trying to sell quack remedies, and hence Italian ciarlatano at first referred to such vendors, and then by extension to any dispenser of impostures. Some etymologists have sought to connect the word with Italian Cerretano, literally ‘inhabitant of Cerreto’, an Italian village supposedly noted for exaggeration, alleging that it may have contributed its suffix to ciarlatano and reinforced its meaning. However that may be, the word reached English in its current form via French charlatan.