Repetition as a rhetorical device - and as the name suggests - consisting of repeating a word or a group of words to produce emphasis, emotion, or clarity. In this specific case, we have a type of repetition called polyptoton, which is the repetition of words derived from the same root. In "We have nothing to fear except fear itself," the word fear is repeated. However, the first time it is used, it is the verb "fear". The second time, it is the noun "fear". Both have the same origin, the same root, but different functions. Still, they refer to the same feeling of being afraid of something. Such repetition emphasizes how powerful fear can be and how we should fight it if we wish to accomplish what we want in life.
