It's an Italian-American slang term based on prejudice/bigotry, and the slang word originated in the United States.
You got that right. You can call my husband "siggie" all day long, and he'll think you're speaking chinese. This is an italo-american term/word/whateveritis. Same goes for "zip". Nobody in Sicily would know what that is.
With regard to Philly (and I know nothing about Philly but this), I know for fact that the Massimino's are related to the Massimino's in Agrigento, Sicily and in Sicily, they are inter-married with the Bruno family. Many Massimino's in Sicily are married to Bruno's.
