You're right, the dark-robed grim reaper is even older than that - Charon is described that way in some references to Greek myth. Maybe one of their jobs was to keep people from wandering into the Land of the Dead?

Makes me wonder if the executioner's hood doesn't reflect it because of humanity's subconscious associations.

I wonder if the guy-in-fedora image is related to the men-in-black phenom in some way as well?