The Yume Yume no Mi is a Paramecia-type Devil Fruit that grants the user the ability to manipulate and control nightmares, turning them into the Nightmare Human (ユメ人間,,Yume Ningen?). It was eaten by...
Yume (ユメ,Yume?) is a Japanese word meaning "dream" or "dreams," and is used here to imply the fruit's connection to nightmares, derived from "Yume" (夢).
This fruit in the anime would be called "Nightmare-Nightmare Fruit"
