The Etymology of "Tuna"
Lynn M. Berk

Tuna - 1900 Spanish American, perhaps related to Latin thunnus, tunnus,
tunny. Name in California for the tunny.

Tunny - 1480 Obscure adaptation of French thon, Provencal ton, or
Italian tonno; Latin thynnus, adaptation of Greek thunnos. A scombroid
fish of the genus Orcynus, especially the common tunny, O. thynnus,
which has been fished from ancient times in the Mediterranean and
Atlantic; it is one of the largest food-fishes.


Source: the Shorter Oxford English Dictionary on Historical Principles,
prepared by William Little, H.W. Fowler, J. Coulson, revised and edited
by C.T. Onions.