From an unused root meaning to break forth; rushing; Perath (i.e. Euphrates), a river of the East -- Euphrates.
H6578. Perath
מְּרָת proper name, masculine, of a river Eupharates, Ευφρατης (Assyrian Purattu DlPa.169 ff., Whence Old Persian, Ufrâtu, SpiegAPK 211); — the greatest river of West Asia; ׳פ Genesis 2:14. פ ׳נְהַר 15:18; (both secondary phrases in J), פ ׳נְהַר also 2 Samuel 8:3 (Qr, see נָהָר), Jeremiah 46:2, 6, 10; Deuteronomy 1:7; 11:24; Joshua 1:4 (D), 2 Kings 23:29; 24:7; 1 Chronicles 5:9; 18:3; נהר omitted Jeremiah 13:4-5, 6, 7 (where Ew Hi Marti, after SchickZPV iii. ll, think of some other מְּרָת, but Gf Gie and most defend Euphrates) 51:63; 2 Chronicles 35:20 (compare Genesis 2:14 above); name not certainly attested before D Jeremiah; on earlier הַנָּהָר for this river see ׳נ.
מֹּרָת Genesis 42:22 see [ מָּרָה].