Thanks, Roberto.
Fifty or more years ago, there were still many immigrants from Naples and environs who retained their language, and finding a translator would not have been difficult in most American cities. Some of the songs were sung by Neapolitans in show business and the tunes if not the words became known to many Americans.

Which reminds me- Italy was a collection of independent countries with many dialects until a revolution brought them together after mid-19th c. Where did 'Italian' as known today come from? I'll have to look that one up.