GAD, in the Bible. 1. A prophet or rather a "seer" (cp. 1 Sam. ix. 9), who was a companion of David from his early days. He is first mentioned in 1 Sam. xxii. 5 as having warned David to take refuge in Judah, and appears again in 2 Sam. xxiv. 11 seq. to make known Yahweh's displeasure at the numbering of the people. Together with Nathan he is represented in post-exilic tradition as assisting to organize the musical service of the temple (2 Chron. xxix. 25), and like Nathan and Samuel he is said to have written an account of David's deeds (1 Chron. xxix. 29); a history of David in accordance with later tradition and upon the lines of later prophetic ideas is far from improbable.
2. Son of Jacob, by Zilpah, Leah's maid; a tribe of Israel (Gen. xxx. 11). The name is that of the god of "luck" or fortune, mentioned in Isa. lxv. 11 (R.V. mg.), and in several names of places, e.g. Baal-Gad (Josh. xi. 17, xii. 7), and possibly also in Dibon-Gad, Migdol-Gad and Nahal-Gad.  There is another etymology in Gen. xlix. 19, where the name is played on: "Gad, a plundering troop (gĕdûd) shall plunder him (yegudennu), but he shall plunder at their heels." There are no traditions of the personal history of Gad. One of the earliest references to the name is the statement on the inscription of Mesha, king of Moab (about 850 B.C.), that the "men of Gad" had occupied Ataroth (E. of Dead Sea) from of old, and that the king of Israel had fortified the city. This is in the district ascribed to Reuben, with which tribe the fortunes of Gad were very closely connected. In Numbers xxxii. 34 sqq., the cities of Gad appear to lie chiefly to the south of Heshbon; in Joshua xiii. 24-28 they lie almost wholly to the north; while other texts present discrepancies which are not easily reconciled with either passage. Possibly some cities were common to both Reuben and Gad, and perhaps others more than once changed hands. That Gad, at one time at least, held territory as far south as Pisgah and Nebo would follow from Deut. xxxiii. 21, if the rendering of the Targums be accepted, "and he looked out the first part for himself, because there was the portion of the buried law-giver." It is certain, however, that, at a late period, this tribe was localized chiefly in Gilead, in the district which now goes by the name of Jebel Jil'ad. The traditions encircling this district point, it would seem, to the tribe having been of Aramaean origin (see the story of Jacob); at all events its position was extremely exposed, and its population at the best must have been a mixed one. Its richness and fertility made it a prey to the marauding nomads of the desert; but the allusion in the Blessing of Jacob gives the tribe a character for bravery, and David's men of Gad (1 Chron. xii. 8) were famous in tradition. Although rarely mentioned by name (the geographical term Gilead is usual), the history of Gad enters into the lives of Jephthah and Saul, and in the wars of Ammon and Moab it must have played some part. It followed Jeroboam in the great revolt against the house of David, and its later fortunes until 734 B.C. (1 Chron. v. 26) would be those of the northern kingdom.
See, for a critical discussion of the data, H.W. Hogg, Ency. Bib. cols. 1579 sqq.; also Gilead; Manasseh; Reuben.
 See G.B. Gray, Heb. Proper Names, pp. 134 seq., 145.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)