Etiology (alternately aetiology, aitiology) is the study of causation. Derived from the Greek αιτιολογία, "giving a reason for" (αἰτία "cause" + -λογία).
The word is most commonly used in medical and philosophical theories, where it is used to refer to the study of why things occur, or even the reasons behind the way that things act, and is used in philosophy, physics, psychology, government, and medicine, and biology in reference to the causes of various phenomena. An etiological myth is a myth intended to explain a name or create a mythic history for a place or family.

Mythology

Eschatology
Geomythology
Just-so story (comparable to etiological myth)