The Greek noun Euphratēs (Εὐφράτης) is the name of the Euphrates River, the longest river in western Asia. It appears twice in Revelation (9:14; 16:12). The name derives from the Hebrew Perāth (פְּרָת), one of the four rivers of Eden (Gen 2:14). In the NT, it marks the boundary of eschatological judgment.
In Revelation 9:14, four angels bound at the Euphratēs are released to kill a third of humanity. In Revelation 16:12, the sixth bowl judgment dries up the Euphrates to prepare the way for 'the kings from the east.' The Euphrates was the eastern boundary of the promised land (Gen 15:18; Deut 1:7) and of the Roman Empire — it symbolized the frontier beyond which hostile powers gathered. John's apocalyptic imagery draws on both the OT associations and the first-century Roman fear of Parthian invasion across the Euphrates.