Unfortunately there's no rule available, for proper names. Accents on toponyms, like in graeca verba, sine lege vagantur.
Just to name a few in my surroundings:
- Albignàsego
- Trebaséleghe
- Sambrusón (it should be Sanbrusón, but that's another matter)
- Grùmolo (delle Abbadesse)
- Bagnòli
- Bagnòlo
Some names have suffixes that help in guessing the right accent, but, as you see from the last three, it's not so easy.
I once saw a list of towns in Calabria: placing the accents was just a wild guess. Some toponyms that are frequently mispronounced are
- San Lazzaro di Sàvena (not Savéna)
- Friùli (not Frìuli)
- Nùoro (not Nuòro)
Family names have the same problem; those derived from job names are usually guessable at, but the region of origin can influence the pronunciation. A family name coming from Veneto and ending in -on or -er should have the accent on the last syllable: Benettón and Venièr; but Mìlan can be rightfully pronounced with the accent on the first syllable, depending on its origin, while Bressàn (it means “from Brescia”) can never be Brèssan.
Just to simplify the matters, every italian word (with more than one syllable) stressed on the last syllable is written with the accent mark. So for “Cesare” you would have the doubt only among two choices. – DaG – 2014-01-05T16:07:30.513