Cf. *ṭirs - molar tooth. There is no direct parallel to this root in Mesopotamian Akkadian, but ṣiršu ‘protuberance’ and ṣurrušu ‘to grow shoots’ are clearly related to it. If one surmises that the meaning “protuberance” is original, we would be faced with a shared semantic innovation in PWS, but in view of ṣa-ra-sa-tum = ZÚ.GUL in VE 227 and related forms discussed in Krebernik 1983:10 and Conti 1990:101, the opposite possibility, viz. semantic marginalization of an original anatomical term in Babylonian, may appear more attractive.