Kerberos is first named in Hes., Th. 311, and he is the same hound of Hades which Homer knows and leaves unnamed… he admits everyone, fawning about them and wagging his tail: but anyone who tries to slip out of Hades again he devours.
Rohde establishes the philological origin of Kerberos in Hesiod and argues that the dog’s primary archaic function was not to terrorize entrants but to prevent exit — fear of entry being a later, secondary elaboration.
, Psyche: The Cult of Souls and the Belief in Immortality among the Greeks, 1894thesis