is properly the Greek name for the land of Edom, which lay to the south of Judea, and extended from the Dead Sea to the Elanitic Gulf of the Red Sea, where were the ports of Elath and Ezion-Gaber. But the Idumaea of the New Testament applies only to a small part adjoining Judea on the south, and including even a portion of that country; which was taken possession of by the Edomites, or Idumaeans, while the land lay unoccupied during the Babylonish captivity. The capital of this country was Hebron, which had formerly been the metropolis of the tribe of Judah. These Idumaeans were so reduced by the Maccabees, that, in order to retain their possessions, they consented to embrace Judaism: and their territory became incorporated with Judea; although, in the time of our Saviour, it still retained its former name of Idumaea, Mark 3:8 . The proper Idumaeans, or those who remained in the ancient land of Edom, became in process of time mingled with the Ishmaelites; the two people thus blended, being, from Nabaioth, or Nabath, the son of Ishmael, termed Nabathaeans; under which names they are frequently mentioned in history. See EDOM .

Bibliography Information
Watson, Richard. Entry for 'Idumaea'. Richard Watson's Biblical & Theological Dictionary. https://www.studylight.org/dictionaries/eng/wtd/i/idumaea.html. 1831-2.

Bible Dictionaries Idumaea

Watson's Biblical & Theological Dictionary

Bible Dictionaries
Idumaea