origin myth

creation myth – Symbolic narrative of how the world began

dindsenchas – Class of onomastic text in early Irish literature

etiology – Study of causation, or origination

just-so story – Unverifiable narrative explanation

List of national founders – List of people credited with creating the state

mythomoteur – Constitutive myth of an ethnic group

national myth – Inspiring narrative about a nation's past

origin story – Plot device

pourquoi story – Narrative that explains why something is the way it is, generally fabulous or mythical