Macrobius, Saturnalia 1.17.64
“They call Apollo Delphios because he shows obscure things in the clarity of light, from making clear (to deloun) things unseen (aphane). Alternatively, as Numenius thinks, they name him so because he is one and alone. For, he says that in the early Greek language, delphon meant one; for this reason, the word for brother is adelphos, as if to signify ‘not one’ [a-delphos].
ἀπόλλωνα Δέλφιον vocant, quod quae obscura sunt claritudine lucis ostendit, ἐκ τοῦ δηλοῦν ἀφάνῆ, aut, ut Numenio placet, quasi unum et solum. Ait enim prisca Graecorum lingua δέλφον unum vocari: unde et frater, inquit, ἀδελφὸς dicitur, quasi iam non unus.
This is absolutely preposterous. I mean, Tzetes-level absurdity.
I love the adelphos one. Here’s one from Eusthathius:
“The story goes that there was a union of a man and women—the husband was named Kêuks. They came to such a level of arrogance, that he wanted to be called Zeus’ name and she submitted herself to be called Hera. Then they started actually doing this. Zeus, because he was outraged by such hubris, changed the people into birds and increased the punishment by compelling them to give birth to their young during winter and near the sea. This is why they are called Al-kuones, because they give birth [kuein] along the sea [ala]….”
Φέρεται γὰρ λόγος, ὅτι συζυγία τις ἀνδρὸς καὶ γυναικός—Κῆϋξ δὲ ὁ ἀνὴρ ἐκαλεῖτο. —ἐς τοσοῦτον ἦλθε φυσήματος, ὡς ἐθέλειν τὸν μὲν Διὸς καλεῖσθαι ὀνόματι, τὴν δὲ τῇ τῆς ῞Ηρας κλήσει καλλωπίζεσθαι. καὶ ἐποίουν μὲν αὐτοὶ οὕτω. Ζεὺς δὲ ἀχθεσθεὶς τῆς ὕβρεως μετάγει τοὺς ἀνθρώπους εἰς ὄρνις καὶ τὸ κακὸν προσαύξων ἀναγκάζει χειμῶνός τε νεοττεύειν αὐτοὺς καὶ περὶ αἰγιαλόν. ὅθεν καὶ ἀλκυόνες ἐκλήθησαν διὰ τὸ παρὰ τὴν ἅλα κύειν.
Despite how preposterous these are, I can at least see how even intelligent people were duped by them; they seem in some ways so unreasonably perfect! Indeed, more vibrant ingenuity was required to develop these false etymologies than seems necessary for the dry labor of tracing the real ones.
More:
Apd. 3.172.4-5
“They named him Achilles, because his lips never touched her breasts. Previously, his name was Ligurôn.”
ὠνόμασεν ᾿Αχιλλέα (πρότερον δὲ ἦν ὄνομα αὐτῷ Λιγύρων) ὅτι τὰ χείλη μαστοῖς οὐ προσήνεγκε.