In Sicily it was common for one family to adopt an Alias or Dictus (Additional surname) usually attached to the end of their true surname to differentiate it from another family in the same town. Usually the two families are related distantly, but far enough back for them not to know how.
This is very common in Carini. In the church records for the town you will often see this written as Cavataio alias Galluzzo or La Barbera vulgo Sevarino.
Here is an example (Bottom right record on page)
Francesco Casalnuovo dictus Finazzo 1881 Marriage
here is a paragraph from a website about this tradition:
In some areas of Italy, a second surname may have been adopted in order to distinguish between different branches of the same family, especially when the families remained in the same town for generations. These alias surnames can often be found preceded by the word detto, vulgo, or dit.
taken from this page: Italian Surnames
Hope that helps.