early 15c., "to contend, fight, struggle," from Latin conflictus, past participle of confligere "to strike together, be in conflict," from assimilated form of com "with, together" (see con-) + fligere "to strike" (see afflict). Meaning "be in opposition, be contrary or at variance" is from 1640s. Related: Conflicted; conflicting.
early 15c., "armed encounter, battle," from Old French conflit and directly from Latin conflictus "a striking together," in Late Latin "a fight, conflict," noun use of past participle of confligere "to strike together, be in conflict," from assimilated form of com "with, together" (see con-) + fligere "to strike" (see afflict).
Meaning "a struggle, a quarrel" is from mid-15c. Sense of "discord of action, feeling, or effect, clashing of opposed principles, etc." is from 1875. Psychological sense of "incompatible urges in one person" is from 1859 (hence conflicted, past-participle adjective); the noun was used from 15c. in the sense "internal mental or spiritual struggle" (against temptation, etc.). Phrase conflict of interest was in use by 1743.
"of or pertaining to conflict," 1950, in psychological writing, from conflict (n.) on model of habitual, etc. Other earlier adjective in more or less the same sense include conflictant (1620s), conflictful (1942), conflictive (1827), conflictory (1817).
"cataclysmic final conflict," 1811, figurative use of the place-name in Revelation xvi.16, site of the great and final conflict, from Hebrew Har Megiddon "Mount of Megiddo," a city in central Palestine, site of important Israelite battles.