False Italianisms in British and American English: A Meta-Lexicographic Analysis by Cristiano Furiassi has a list of selected false Italianisms. Lest there be any doubt about what it’s meant by false Italianisms, here it is in the autor’s own words:
False Italianisms – which most English speakers believe to be purely Italian – are created when genuine lexical borrowings from Italian are so reinterpreted by a recipient language, English in this case, that native speakers of Italian would not recognize them as part of their own lexical inventory and would neither understand nor use.
And here is a selection of the selection. Opening the list we have:
In English it means in the open air. To express the same idea in Italian you’d say all’aperto (in the open). Fresco is Italian for fresh (of fruit), recent (news), pleasantly cool, etc.
Now in Italain confetti (singular, confetto) are sugar-coated almonds, pistachios, etc; or pills. The little, brightly coloured papers are coriandoli (plural of coriandolo, also coriander).
This in Italian for hell. A large fire in Italian would be incendio.
is Italian for milk. If you want a mixture of coffee and milk in Italy ask for a latte macchiato (stained milk) or a caffellatte.
Pepperoni or peperoni
Ask for peperoni (singular, peperone) in Italy and you’ll get peppers. If it is the spicy sausage you want ask for salame piccante instead.