The river of Hate, called by Milton “abhorrëd Styx, the flood of burning hate” (Paradise Lost, ii. 577). It was said to flow nine times round the infernal regions. (Greek, stugeo, hate.)
The Styx is a river of Egypt, and the tale is that Isis collected the various parts of OsIris (murdered by Typhon) and buried them in secrecy on the banks of the Styx. The classic fables about the Styx are obviously of Egyptian origin. Charon, as Diodorus informs us, is an Egyptian word for a “ferryman,” and styx means “hate.”
“The Thames reminded him of Styx.” —M. Taine.
Styx, the dread oath of gods.
“For by the black infernal Styx I swear (That dreadful oath which
binds the Thunderer) `Tis fixed!”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894