Genesis 25:16

By their castles; or, the castles, towns, and tribes of principal note, received their names from these twelve princes, or phylarks, whose authority is still recognized among all the tribes of the Arabs. (Thevenot.) (Haydock) --- The towns of these people were easily built, and more easily destroyed; for they consisted only of tents, Jeremias xlix. 31. Their castles were perhaps only sheep-folds, as the original Tiroth may signify; or they were a sort of watch-towers, to prevent the sudden attack of an invading enemy, and to serve also for a retreat. (Calmet)