Naggoob is the Father of Ghouls and the free lead sevant of Nyogtha, according to the Book of Eibon. (EXP: "The Horror in the Gallery") Nug, Feaster Among the Tombs, is the grandfather of all ghouls who serve Nyogtha. (EXP: "The Descent into the Abyss")
Behind the Mythos
When creating Naggoob for the 1976 "Horror in the Gallery" story, Lin Carter seemingly forgot that Lovecraft already conceived Shaurash-ho, a descendant of Nug, as the ancestor of Yogash the Ghoul in his Family tree of Azathoth.
By stating Nug to be grandfather of the same ghouls in his 1980 story "Descent into the Abyss", he seemingy made Nagoob and Shaurash-ho one and the same. "Naggoob" being the Hyperborean alternative name would solve this seeming error.