Since then, I discovered that it is a title of Jupiter in Virgil's Aeneid (I'll quote this at a later time); it seems to be the title of the highest God in an ancient pantheon--as Jupiter is to the members of his divine council, so YHWH to his.
Interestingly enough, Augustine argues this is just a matter of semantics:
The Platonists may prefer to call those good angels "gods" rather than "demons," and to include them among those whom Plato, their founder and master, writes of having been created by the supreme God. They may do as they like; there is no need for us to engage in a tiresome dispute about words. If they mean that they are immortal, but, at the same time, created by the supreme God and that they are blessed, not by themselves, but through adhering to him who made them, then their meaning is the same as ours, whatever title they use. That this is the opinion of the Platonists, or at least of the better Platonists, can be proved by their writings. As for the actual title, the fact that they give the name "gods" to creatures who are immortal and blessed in the above sense, there is here not dispute between us, simply because one can find in our sacred Scriptures such quotations as "The Lord, the lord of gods, has spoken," and in another place: "Give thanks to the God of Gods," and "a great king above all gods." (Augustine, City of God 9.23; trans. Henry Bettenson)
And he goes on, piling on examples, the latter of which are places in which God refers to humans as gods. But the gist is we say angel, you say god, but we all mean the same thing: there may be a different "signum" but the same "res." Or, sort of. He only really agrees with the Platonists (or the better ones), and Platonizes the biblical sense with a post-Nicene sentiment in the process. I dare think the biblical terminology interacted not with Platonic thought, but with mythic thought (using "myth" in its original meaning, not its pejorative sense). It is probably more in line with the tales that Augustine rejects: Jupiter in the Aeneid. Or better yet, the collective Anunnaki in ancient Babylonian thought. The post-Nicene coloration can be seen in the emphasis on creator/creature. Augustine is willing to concede the terminology only insofar as the Platonists recognize these beings as created. I personally do not see such an emphasis in the biblical texts Augustine cites. In the Nicene Creed, Jesus' high status is emphasized because he is "begotten, not made." The "made" in this terminology distinguishes divinity from non-divinity. Thus, if the Platonists refer to their "gods" as "made," then Augustine won't make a fuss about calling them "gods"--as long as they recognize the substance of being as made rather than maker. Earlier texts make occasionally make this distinction, but I do not think this distinction was particularly widespread or given such a privileged position of a litmus test until 325 CE, and definitely not particularly relevant for biblical literature. The litmus test I see in earlier literature is not necessarily creator/creature (it may be there, but is not decisive), but of worship: you only worship the "God of Gods," the highest one up there. But, then again, that is not necessarily monotheism, but monolatry. Nonetheless, I would happy to be shown that I am wrong.
