"qualified or trained to fight," mid-14c., present participle adjective from fight (v.). Fighting chance is from 1877; fighting mad is attested by 1750; fighting words is by 1882. Fighty "pugnacious" is attested from c. 1200.[fighting etymology, fighting origin, 英语词源]
early 13c., "act of engaging in combat," verbal noun from fight (v.). Old English had feohtlac (n.) "fighting, battle." Nautical fighting-top "platform near the top of a mast for small-arms fire" is from 1890.