2. A blood feud between families started by the killing of a member of one family that is then avenged by the killing of a member of the other family: The vendetta between two branches of the family had lasted so many years that no one actually remembered how it started or what it was all about.
3. Etymology: from Italian vendetta, "a feud, a blood feud"; from Latin vindicta, "revenge"; "vindictive"; from vim dicare, "to show authority"; from vim, accusative of vis, "force" + root of dicere, "to say".
English speakers borrowed vendetta from Italian, from which it ultimately traces to the Latin verb vindicare, "to lay claim to" or "to avenge". That Latin word is also in the family tree of many other English terms related to "getting even"; including avenge, revenge, vengeance, vindicate, and vindictive.