Vendetta is a noun pronounced ven-'de-tê. Italian has given the English lexicon of almost all of classical music its words such as allegro, brio, forte, piano, pizzicato, sotto voce and so on. In more recent times the Italian language has contributed to the English lexicon by giving it the names of many delicious foods and foodstuffs such as ciabatta, chianti, lasagna, macaroni, pasta, and spaghetti. Not to mention the popularity or notoriety of organized crime, both in real life and in fiction, has given us a full of variety of additions by the likes of capo, cosa nostra, mafia, omerta and this word the vendetta. It is derived from :
    "(The) Italian reflex of Latin vindicta "revenge, vengeance" from vindicare "assert one's authority, avenge." This verb is from vim, accusative of vis "power, strength" + dicere "say, speak." Latin dictatum "dictated," from the same root, became dite "literary piece" in Old French where it was nicked by the English who use it today as "ditty." The same root that provided Latin dic- also gave Germanic *taik-jan from which Old English tæc-an "to show, instruct" and Modern English "teach" derive. "(B. L. Loureiro yourdictionary.com)

The idea of vendettas arose originally among quarrels between families in Corsica where a relation of a murder victim would seek retribution of the death by killing the murderer or someone in the murderer's family.The February 2002 Smithsonian Magazine tells:

    It is no accident that the term "vendetta" is the only Corsican word to have passed unchanged into the dictionaries of most of the world's languages. Blood feuds were still going strong only a generation or so ago and continue even today. "You must never forget," one observer admonishes, "that the vendetta was, for thousands of years, the only law a Corsican could trust."
This has also come to mean in today's usages metaphorically as in a prolonged dispute or a campaign where there is vexation, wit or a constant criticism of a person. Whereas blood is no longer literally spilled; verbal massacres count, as well. While vendettas are no longer prevalent in Corsica there were some rather well known ones in the Ozark Mountains where many a family feuds erupted among the moonshiners and continued up until the Civil War. Elsewhere among criminal organizations they still occasionally erupt. Participants are vendettists. No longer found among the nations of Europe, but still a way of life in the Caucasus where clan life in a Chechen mountain village today revolves around raising sheep and raiding. The clans practice the classic blood-vendetta where no offense against clan honor goes unpunished, and feuds go on for generations.

Sources:

BLOODY WILLIAMSON:
http://www.prairieghosts.com/bloody_will.html

Chechen Nationalism and the Tragedy of the Struggle for Independence:
call.army.mil/fmso/

Smithsonian Magazine :
http://www.smithsonianmag.si.edu/

yourdictionary:
http://www.yourdictionary.com/