"Socrates: My notion would be something of this sort:- I suspect that the sun, moon, earth, stars, and heaven, which are still the Gods of many barbarians, were the only Gods known to the aboriginal Hellenes. Seeing that they were always moving and running, from their running nature they were called Gods (Theous) or runners (Theontas); and when men became acquainted with the other Gods, they proceeded to apply the same name to them all. Do you think that likely? Hermogenes: I think it very likely indeed."
In brief, "theoi" (gods) is ultimately derived from the verb "theo", meaning to run, and designating motion.