Meaning

noun a crime syndicate in the United States; organized in families; believed to have important relations to the Sicilian Mafia

noun a secret terrorist group in Sicily; originally opposed tyranny but evolved into a criminal organization in the middle of the 19th century

noun any tightly knit group of trusted associates

originBorrowed from Italian mafia, of uncertain origin. In the first instance, it is not clear whether the lemma in question is a Sicilian exonym or endonym, since written and oral sources on this term are scarce, the etymology remains uncertain and it's worthy of further investigation. It is possibly a regional term of the then recently established Kingdom of Italy; thus the meaning "spirit of…

Etymology from Wiktionary, CC BY-SA 3.0