Adam Clarke on Jeremiah 49:8

Dwell deep - An allusion to the custom of the Arabs, who, when about to be attacked by a powerful foe, strike their tents, pack up their utensils, lade their camels, which they can do in a couple of hours, and set off to the great desert, and so bury themselves in it that no enemy either will or can pursue, as it is the Arabs alone that know the deserts, and can find water and provender for their support.

Dedan - Was a city of Idumea, not far from Teman.