The Wicked Stepmother

We are all familiar with the wicked stepmother character in fairy-tales (Cinderella, etc.). While the Brothers Grimm, those famous collectors of tales (and linguists!), surely had some hand in it, this representation of the stepmother seems to have much wider traction.

There exists already very early in the Greek tradition the concept of a proverbially cruel stepmother. By the time of Hesiod, the stepmother (μητρυιὴ) has distilled, essentially, into a single word formula for cruelty. In the conclusion of Works & Days (822-28):

Αἵδε μὲν ἡμέραι εἰσὶν ἐπιχθονίοις μέγ' ὄνειαρ·

αἱ δ' ἄλλαι μετάδουποι, ἀκήριοι, οὔ τι φέρουσαι.

ἄλλος δ' ἀλλοίην αἰνεῖ, παῦροι δὲ ἴσασιν.

ἄλλοτε μητρυιὴ πέλει ἡμέρη, ἄλλοτε μήτηρ.

τάων εὐδαίμων τε καὶ ὄλβιος ὃς τάδε πάντα

εἰδὼς ἐργάζηται ἀναίτιος ἀθανάτοισιν,

ὄρνιθας κρίνων καὶ ὑπερβασίας ἀλεείνων.

Some days are a great benefits to men on earth,
But others are indifferent, harmless, bringing nothing at all.
Someone praises one kind of day, but few understand them.
Sometimes a day is a stepmother, sometimes a mother.
He is fortunate and blessed of men, who
knowing all these things, works on, guiltless in eyes of the gods,
discerning omens of flight and avoiding transgressions.

The juxtaposition of the mother (μήτηρ) establishes a polar relationship, i.e, cruel : caring. But this minor contextualization is unnecessary for Aeschylus in the 5th century (PB 725-27):

ἵνα

τραχεῖα πόντου Σαλμυδησσία γνάθος,

ἐχθρόξενος ναύτῃσι, μητρυιὰ νεῶν.

...where
Salmydessa is, the jagged jaw of the sea,
A hateful host for sailors, the stepmther of ships.

A pan-Indo-European theme? Even broader? I need to do some more investigating.