The character is believed to have originated as Gironi da Crina (in Ligurian) or Geralmo della Scrofa (in Italian), c. 1630 in Genoa.
In the early 19th century, a puppeteer by the name of Giovanni Battista Sales got into trouble with the authorities who did not appreciate his sarcastic humor or the fact that the character had the same first name as a brother of Napoleon, who had invaded the region.
Sales fled to Callianetto, a hamlet of Castell'Alfero, east of Turin and just north of Asti, and changed the name of the character to the Piedmontese Gioann dla Doja (later Giandoja and Piedmontenize as Gianduja), which means something like "John of the Jug" (with doja meaning "tankard" or "beer mug", as the character was fond of drinking).
In the commedia dell'arte, Gianduja is a fond drinker and a very lecherous character, and Giacometta, his lover, always becomes jealous of him.
He is dressed (in the usual version) with a tricorn hat and a brown jacket with red borders.