Revenge
late Middle English: from Old French revencher, from late Latin revindicare, from re- (expressing intensive force) + vindicare ‘claim, avenge’.
wiktionary
From Middle French revenge, a derivation from revenger, from Old French revengier (possibly influenced by Old Occitan revènge(“revenge, comeback”), from Old Occitan revenir(“to come back”)), a variant of Middle French revancher, from Old French revenchier. The variants Old French vengier (whence French venger) and Old French venchier are both descended from Latin vindicō, with stress-conditioned different parallel development in the inflectional forms. Compare avenge and vengeance.
etymonline
revenge (v.)
late 14c., revengen, "avenge oneself," from Old French revengier, revenger, variants of revenchier "take revenge, avenge" (13c., Modern French revancher), from re-, here perhaps an intensive prefix (see re-), + vengier "take revenge," from Latin vindicare "to lay claim to, avenge, punish" (see vindication). Transitive sense of "take vengeance on account of" is from early 15c. Related: Revenged; revenging; revengement.
To avenge is "to get revenge" or "to take vengeance"; it suggests the administration of just punishment for a criminal or immoral act. Revenge seems to stress the idea of retaliation a bit more strongly and implies real hatred as its motivation. ["The Columbia Guide to Standard American English," 1993]
revenge (n.)
"retaliation for wrongs real or fancied, act of doing harm or injury in return for wrong or injury suffered," 1540s, from French revenge, a back-formation from revengier (see revenge (v.)). Hence "vindictive feeling, desire to be revenged."
