The patriarch Jacob loved his wife Rachel, but it was his wife Leah who initially made him a father (since Rachel was unable to conceive for many years). When Rachel presented her handmaiden Bilhah to Jacob as a wife, in order that she might serve as a surrogate mother to Bilhah’s children, Leah felt herself put at a distinct disadvantage. While she had already borne Jacob four sons, she had not conceived recently and worried that her children would become outnumbered.
Leah therefore followed her sister’s example and presented her own handmaiden, Zilpah, as a wife to Jacob. Zilpah quickly conceived. When Leah saw that her plan had been successful, she announced: “Good luck has come!” and named the boy, Gad.
“Luck,” however is only one interpretation of the name Gad. The Biblical commentator Abraham Ibn Ezra (Spain 1089 – c.1164) maintained that the name Gad was related to the word g’dood, meaning troop, and commented that Leah now had a “troop” of children. Rabbi Samson Raphael Hirsch (Germany, 1808-1888) brought the two meanings of Gad together when he noted that a g’dood is a raiding troop, one that moves swiftly and unexpectedly. Rabbi Hirsch noted that since gad also means chance (luck), “here too bah gad probably means: an unexpected piece of luck has come. This son was one for whom, in ordinary circumstances, she could not have reckoned.”
The interpretation of Gad as a troop is also related to what Jacob stated at the end of his life. When Jacob blessed his children on his death bed in Egypt, he said of Gad: “Gad, a troop shall troop upon him; and they shall troop upon their heel” (Genesis 49:19), which implies that Jacob saw in his son significant military characteristics and aptitude.