One panelist explained that his goblins, like the rest of the less familiar creatures in his work, came from Pliny. Based on a theory that we had contact with a world with such beings every thousand years.
The alien, the strange monster -- and then the more eerie half-human one.
And how monsters get altered for the time. After all, modern day zombies are medieval vampires, but the original zombie, who isn't a danger to meet but to become, doesn't appear in modern fiction.
The usefulness of zombies for guilt-free killing.