ṭᵃhar - 1. on, above; 2. in addition, besides (LS 200; CSOL I 684; CSOL II 617; Naumkin et al. 2015a:90)

The original anatomical meaning is completely lost throughout this group. Semantically similar prepositional use of reflexes of *ṯ̣a(h)r- is admittedly attested in a few other Semitic languages (SED I No. 284). (Kogan 2015:575)