Answer:
The origin stories are the stories which provide us about the established background narrative informing us about the identity of the characters which might be a fiction or a science related concept. But scientific theories of origin only tell us about the origin of concepts related to sciences which might be human life, or origin of earth etc.
But the similarity between the two is when both the stories speak about the origin of concepts related to science like origin of life on earth is an origin story and a scientific theory of origin also.