She called his name Gad - This has been variously translated. גד gad, may signify a troop, an army, a soldier, a false god, supposed to be the same as Jupiter or Mars; for as Laban appears to have been, if not an idolater, yet a dealer in a sort of judicial astrology, (see Genesis 31:19), Leah, in saying בגד bagad, which we translate a troop cometh, might mean, By or with the assistance of Gad - a particular planet or star, Jupiter possibly, I have gotten this son; therefore she called him after the name of that planet or star from which she supposed the succor came. See note on Genesis 31:19. The Septuagint translate it εν τυχη, with good fortune; the Vulgate, feliciter, happily; but in all this diversity our own translation may appear as probable as any, if not the genuine one, בא גד ba gad, for the keri, or marginal reading, has it in two words, a troop cometh; whereas the textual reading has it only in one, בגד bagad, with a troop. In the Bible published by Becke, 1549, the word is translated as an exclamation, Good luck!

And Leah said, (d) A troop cometh: and she called his name Gad.
(d) That is, God increases me with a multitude of children for so Jacob explains this name Gad (Genesis 49:19).

And Leah said, a troop cometh,.... A troop of children, having bore four herself, and now her maid another, and more she expected; or the commander of a troop cometh, one that shall head an army and overcome his enemies; which agrees with the prophecy of Jacob, Genesis 49:19,
and she called his name Gad: which signifies a "troop", glorying in the multitude of her children, that she had or hoped to have.