ὤδινεν ὄρος, Ζεὺς δ' ἐφοβεῖτο, τὸ δ' ἔτεκεν μῦν → the mountain was in labor — even Zeus was afraid — but gave birth to a mouse

[billberg23]

ὤδινεν ὄρος, Ζεὺς δ' ἐφοβεῖτο, τὸ δ' ἔτεκεν μῦν → the mountain was in labor — even Zeus was afraid — but gave birth to a mouse (Theopompus, Sotades, etc.).
Cf. Galen, Corpus medicorum Graecorum, vol. 5.9: "But that story is like the old saying we learned in childhood, 'The mountain labored but gave birth to a mouse (ὤδινεν ὄρος καὶ ἔτεκε μῦν)'."

[spiros]

Another variation: Ὤδινεν ὄρος, εἶτα μῦν ἀπέτεκεν
Variant translation: The mountain was in labor, then it gave birth to a mouse.