Nergal-Beasts don't have names. They had no need for one. For all Nergal-beasts eventually fuse with their host's mind, the Nergal-beast is often given a nickname by its new host as they were not born with Nergal blood and therefore not use to having a symbiote.

Minnie's memories chewing at his mind, the Nergal clawing for control, Mandy's coldness, Grim's frequent absence, and now drowning himself in bounty hunting and alcohol…