prolegomenon
A prefatory discussion; a formal essay or critical discussion serving to introduce and interpret an extended work.
Frye here is not rewriting myth as some assume. Her prolegomenon is intended to be read as fiction not autobiography.
Where it comes from
From the Ancient Greek neuter noun: προλεγόμενον (prolegómenon, “that which is said beforehand,”) [plural: προλεγόμενα (prolegómena), from the verb: προλέγω (prolégō, “I say before[hand]”)] referring to an introduction.
Adapted from the Wiktionary entry prolegomenon (CC BY-SA 4.0).