What is the origin of vendetta?

Vendetta “a prolonged and bitter feud” is a borrowing from Italian, derived from Latin vindicta “vengeance,” from vindex “defender,” which is also the source of avenger, revenge, vengeance, and vindicate. Vindex is likely a compound of vīs “energy, force” and the agentive suffix -dex, roughly meaning “shower, proclaimer.” Vīs is the source of vim (as in the phrase vim and vigor), violate, and violent—all of which literally pertain to a demonstration of strength or force—while the suffix -dex is related to the verbs dicāre “to proclaim, assign” (compare abdication, dedicate, and predicament) and dīcere “to say, tell” (compare dictionary, valedictorian, and verdict). Vendetta was first recorded in English in the early 1850s.