Origin and history of vindicate

mid-15c., vendicacion, "act of avenging, revenge; assertion of a claim" (senses now obsolete); 1640s as "justification by proof, defense against censure;" from Old French vindicacion "vengeance, revenge" and directly from Latin vindicationem (nominative vindicatio) "act of claiming or avenging," noun of action from past-participle stem of vindicare "lay claim to, assert; claim for freedom, set free; protect, defend; avenge" (related to vindicta "revenge"). This is held to be probably from vim dicare "to show authority," from vim, accusative of vis "force" (see vim) + dicare "to proclaim" (see diction).

c. 1300, vengeaunce, "retribution, punishment, revenge," from Anglo-French vengeaunce, Old French vengeance, venjance "revenge, retribution" (12c.), from vengier "take revenge," from Latin vindicare "assert a claim, claim as one's own; avenge, punish" (see vindicate). Alternative vengement is attested from mid-14c.

Vengeance is mine, ... saith the Lord. Therefore if thine enemy hunger, feed him; if he thirst, give him drink; for in so doing thou shalt heap coals of fire upon his head. [Paul to the Romans, xii:19-20]