Arnon

"Swift, the southern boundary of the territory of Israel beyond" "Jordan, separating it from the land of Moab (Deut. 3:8, 16)." This river (referred to twenty-four times in the Bible) rises in "the mountains of Gilead, and after a circuitous course of about" 80 miles through a deep ravine it falls into the Dead Sea nearly opposite Engedi. The stream is almost dry in summer. It is now called el-Mujeb. The territory of the Amorites extended from the Arnon to the Jabbok.

Definition of Arnon:
"rejoicing; sunlight"