Answer:
In Greek mythology Prometheus was a Titan. The Titans were the Gods that were in charge before the Olympians took over. Prometheus sided with the Olympians in the war of succession but after wards was considered to be something of a poor cousin. He is the one credited with the creation of man from earth -- hence the equating with Dr. Frankenstein. Also Prometheus came to a bad end (he stole fire from the Gods to give to men which offended Zeus. So he got chained to a rock with an eagle visiting him every day and eating out his liver.) So the association is also an ominous one.