What does "hickory" mean?

Hickory: An American tree of the genus Carya, of which there are several species. The shagbark is the C. alba, and has a very rough bark; it affords the hickory nut of the markets. The pignut, or brown hickory, is the C. glabra. The swamp hickory is C. amara, having a nut whose shell is very thin and the kernel bitter. Hickory shad. (Zoöl.) (a) The mattowacca, or fall herring. (b) The gizzard shad.