Берешит 14:3 Комментарий: Rashi, Sforno, Radak & Siftei Chakhamim

עמק השדים VALE OF SIDDIM — So it was named because it contained many fields (שדות)

כל אלה, all the ones just named, Amrafel and the two groups that conducted the war.

כל אלה, the four against the five.

There are many Midrashic explanations of this name. הוא ים המלח THE SAME IS THE SALT SEA — After some time the sea flowed into it (the vale) and thus the Salt Sea came into existence. The Midrashic explanation states that the rocks that surrounded it had cracked and streams thus flowed into it (Genesis Rabbah 42:5).