The Isle of Grub was an island on the planet Ferenginar.
It is infamous as the location of the Isle of Grub Festival, where following the cancellation of a performance by the musical group Success, rioters injured a hundred thousand fans, and every structure on the isle was burned to the ground. (DS9 reference: Legends of the Ferengi)
Yrena had shell accounts on the Isle of Grub. (DS9 eBook: I, The Constable)