Probably šamadtā -> šamattā; for which see s.v. šmdh, šmdtˀ n.f. For an alternative view and latest bibliography see Y. Paz, "Banned and Branded: The Mesopotamian Background of Šamata", Aramaic Studies (2021):1-12. If that study is on the right track, we would assume that the borrowing came from the noun šimtu "brand, mark" rather that the related verb. But we doubt it. See our note s.v. šmd vb.