The bank or bench was the counter on which shopkeepers of yore displayed their goods. Streetvendors used to mount on their bànk to patter to the public. The French word is “saltim banque;” and the Italian word “Cantambanco ” (i.e. canta in lanco, one who patters from his bank).
In Italian, montambanco (a quack-doctor) is also in use.
“... Se disant estre quelque trabe. ou quelque Juif convert, il se feignoit medecin du roi de Perse, et comme tel il montoit la banque. C'estoit la que, pour debiter ses drogues, il etourdissoit de son babil toute l'assemblée.” —Histoirc Generale des Larrons, book i. chap.xxix.
There were temporary mountebanks as well as more regular merchants. In Attica, the names of Dolon and Susarion of Icaria are distinguished. In France, Tabaria, Tabarin, Turlupin, Gauthier-Garguille,
Gros-Guillaume, Guillot-Gorju, Bobêche, Galimaufré, and Gringalet (a marvellous number of G's). In England, Andrew Borde, and some few others of inferior note.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894