In the past, when many physical phenomena were not well understood or when histories were not recorded, myths often arose to provide etiologies. Thus, an etiological myth, or origin myth, is a myth that has arisen, been told over time or written to explain the origins of various social or natural phenomena. For example, Virgil’s Aeneid is a national myth written to explain and glorify the origins of the Roman Empire. In theology, many religions have creation myths explaining the origins of the world or its relationship to believers.
Source: Etiology – Wikipedia