Jastrow: גַּד II

גַּד II m. (b. h.; cmp. כַּד II) a rounded-off seed grain, coriander, (in Talm. a. Midr.) linseed. Yoma 75ᵃ (ref. to Ex. XVI, 7) עגול כגִידָּא וכ׳ the manna resembled a grain by its rounded shape, and a pearl by its white color; even so it has been taught גד שדומה לזרע וכ׳ the word gad (grain) is used, because the manna resembled linseed; Yalk. Ex. 261; Num. 734. Mekh. B’shall., Vayassa, 5 (ref. to Ex. l. c.) איני יודע של מי דומה I do not know to which the comparison refers (to shape or to color); … דומה לזרע וכ׳ it resembles (in form) linseed: but you might think &c., ת"ל לבן therefore ‘white’ is added.