Meaning

noun important warm-water fatty fish of the genus Thunnus of the family Scombridae; usually served as steaks

noun any very large marine food and game fish of the genus Thunnus; related to mackerel; chiefly of warm waters

originFrom Middle French thon + -y, from Old Occitan ton, from Latin thunnus, from Ancient Greek θύννος (thúnnos).

Etymology from Wiktionary, CC BY-SA 3.0