And Achish said, Whither have ye made a road to day? And David said, Against the south of Judah, and against the south of the Jerahmeelites, and against the south of the Kenites. (1 Samuel 27:10)
Literally, “the Negeb of Judah” (see on Gen. 12:9). The area occupied by these tribes lay within the Negeb. Thus, while David was raiding in the “Negeb of Judah,” he was not fighting against his own people, but with foreign peoples who had trespassed on Judah’s territory. At the same time his statement was sufficiently ambiguous to permit Achish to interpret it otherwise.
Jerahmeelites.
Jerahmeel was the first-born son of Hezron, the grandson of Judah (1 Chron. 2:9, 25. He was probably born after Jacob went to Egypt, for he is not mentioned among the 70 persons of Jacob’s household who migrated to Egypt (Gen. 46:12). It is not certain whether this clan accompanied Israel in the Exodus movement or not. They seem to have settled in the region south of Hebron. They probably lived as nomads, and took no part in the national affairs of Israel.