pleonasm

Pleonasm, which stems (via Late Latin) from the Greek verb pleonazein, meaning "to be excessive," is a fancy word for "redundancy." It's related to our words plus and plenty, and ultimately it goes back to the Greek word for "more," which is pleōn. Pleonasm is commonly considered a fault of style, but it can also serve a useful function. "Extra" words can sometimes be helpful to a speaker or writer in getting a message across, adding emphasis, or simply adding an appealing sound and rhythm to a phrase—as, for example, with the pleonasm "I saw it with my own eyes!"