From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Gad. (A Troop).

1. Jacob's seventh son, the first-born of Zilpah, Leah's maid, and whole-brother to Asher.  Genesis 30:11-13;  Genesis 46:16;  Genesis 46:18. (B.C. 1753-1740).

2. "The Seer", or "The King'S Seer", that is, David's seer  1 Chronicles 29:29;  2 Chronicles 29:25, was a "prophet" who appears to have joined David when in the old.  1 Samuel 22:5. (B.C. 1061). He reappears in connection with the punishment inflicted for the numbering of the people.  2 Samuel 24:11-19;  1 Chronicles 21:9-19. He wrote a book of the Acts of David,  1 Chronicles 29:29, and also assisted in the arrangements for the musical service of the "house of God."  2 Chronicles 29:25.

Webster's Dictionary [2]

As a prefix ad- assumes the forms ac-, af-, ag-, al-, an-, ap-, ar-, as-, at-, assimilating the d with the first letter of the word to which ad- is prefixed. It remains unchanged before vowels, and before d, h, j, m, v. Examples: adduce, adhere, adjacent, admit, advent, accord, affect, aggregate, allude, annex, appear, etc. It becomes ac- before qu, as in acquiesce.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [3]

according to Arabian traditions, was the son of Udh, or Uz (the grandson of Shem,  Genesis 10:23), and the progenitor of a powerful tribe called the Adites, who settled in Er-Raml, or Sandy Arabia (Abulfeda, Hist. Anteislam. p. 17, ed. Fleischer). Like the other kindred tribes of those early times, the Adites soon abandoned the true worship of God, and set up four idols whom they worshipped: Sakia, whom they imagined to supply rain; Hafedha, who preserved them from all foreign and external dangers; Razeka, who provided them with food; and Salema, who restored them from sickness to health (Sale's Koran, p. 122, note). It is said that God commissioned the prophet Hud or Heber to attempt their reformation, but, remaining obstinate in their idolatry, they were almost all destroyed by a suffocating wind. The few who escaped retired with the prophet Hud to another place. Before this severe punishment they had been visited with a dreadful drought for four years, which killed their cattle, and reduced them to great distress (see D'Herbelot, Bibl. Or. s.v. Houd). They are often mentioned in the Koran, and some writers, on the authority of that work, affirm that they were of gigantic stature. (See Arabia).