Italian surnames have changed so much in the past century.  Almost everyone I meet has a story about how their surname was changed at Ellis Island upon their ancestor's entry in to the US.  The truth of the matter is that names were not usually changed at Ellis.  Manifest lists were complied and written in the country from which the immigrant came and by someone who normally was familiar with the language of that same traveler.  So how did the names change then?
Names changed for several reason. One such reason was that the immigrant was illiterate and so they could not spell their last name. This resulted in the dropping of some double letters in surnames or in silent letters. Before 1909, passports were not usually used or needed so it was not uncommon for minor spelling errors to occur.  You may wonder about birth certificates as well but it was not normal custom for Italians to carry a copy of their birth certificates on them. In fact, rarely did any see their actual birth acts unless they were getting married in Italy and their parents were deceased and in which case they were required to show a copy of their births upon registering to get married.  Of course, many immigrants left Italy as young, single men and so had no reason to ever really see their birth records.  Not only could this cause issues with the correct spelling of a surname, but also with birth dates as often the actual day a child was born and the day a child was registered were different.
This was not the only reason a surname might change. Some changed their surnames to something that was more Anglicized to help secure work and discourage discrimination.   The process was a simple one as no legal documents were necessary.  Giovanni Rossi might become John Ross and Vincenzo Valentino might be known as James Valentine.  This name change usually only affected the person in the US.  He would still be known by his birth name on legal documents or upon traveling.
I will write more on why names changed or how they changed in upcoming posts. Meanwhile, I would be interested in hearing how your name has changed or why it changed.