Jabbok - (Easton's Bible Dictionary)
A pouring out, or a wrestling, one of the streams on the east of Jordan, into which it falls about midway between the Sea of Galilee and the Dead Sea, or about 45 miles below the Sea of Galilee. It rises on the eastern side of the mountains of Gilead, and runs a course of about 65 miles in a wild and deep ravine. It was the boundary between the territory of the Ammonites and that of Og, king of Bashan (Josh. 12:1-5; Num. 21:24); also between the tribe of Reuben and the half tribe of Manasseh (21:24; Deut. 3:16). In its course westward across the plains it passes more than once underground. "The scenery along its banks is probably the most picturesque in Palestine; and the ruins of town and village and fortress which stud the surrounding mountain-side render the country as interesting as it is beautiful." This river is now called the Zerka, or blue river.