Here we have three accounts: Aristotle, Plato and Hesiod, on the etymology of aether. Despite being the non-philosopher, with typically non-rational, mythological explanations, guess who comes closest to the correct explanation as originating from aitho (αἴθω) light up, kindle and in the passive (αἴθομαι) burn, blaze? On a related and decidedly politically incorrect note, the Greek name for Ethiopians is literally “[sun]burnt face.”

We call the substance of the heaven and stars “aether,” not as some do, because it burns (aithesthai), being fire-like, although they are wrong about this ability, which is confused for fire’s, but because it is always moving (aei thein), being carried in a circular motion, being an element different than the four, unmixed and divine. (Aristotle, On the Cosmos, 392a) [1]

I construe “aether” in this way, that it is always running (aei thei), because it flows around the air (aera reon), so it would justly be called aeitheer. (Plato, Cratylus, 410b) [2]

and in turn Aether and Day came forth from Night,
whom she gave birth to after mingling in love with Erebus…
(Hesiod, Theogony, 124-125) [3]

We can see here that, although not explicit, Hediod’s account, which pairs Day and Aether together, clearly considers Aether to be something like “shining” or “brightness,” in contrast to the blackness of Night, from which every day, and its light, comes forth.

Hesiod appears to be the clear winner, although to be fair, Aristotle is usually not taken to be the author of On The Cosmos.

REFERENCES

[1] Οὐρανοῦ δὲ καὶ ἄστρων οὐσίαν μὲν αἰθέρα καλοῦμεν, οὐχ, ὥς τινες, διὰ τὸ πυρώδη οὖσαν αἴθεσθαι, πλημμελοῦντες περὶ τὴν πλεῖστον πυρὸς ἀπηλλαγμένην δύναμιν, ἀλλὰ διὰ τὸ ἀεὶ θεῖν κυκλοφορουμένην, στοιχεῖον οὖσαν ἕτερον τῶν τεττάρων, ἀκήρατόν τε καὶ θεῖον.

[2] τὸν δὲ αἰθέρα τῇδέ πῃ ὑπολαμβάνω, ὅτι ἀεὶ θεῖ περὶ τὸν ἀέρα ῥέων ἀειθεὴρ δικαίως ἂν καλοῖτο.

[3] Νυκτὸς δ᾿ αὖτ᾿ Αἰθήρ τε καὶ Ἡμέρη ἐξεγένοντο,
οὓς τέκε κυσαμένη Ἐρέβει φιλότητι μιγεῖσα..