Notes: The EC-WC comparison seems compelling, but the hushing *ǯ in PWC raises some problems. The reconstruction of *ǯ is based on the correspondence Ub. ʒ : PAT *ʒ́. It is not excluded, however, that the original PAT form *(a)ʒV underwent an influence of other roots: PAT *śǝ 'snow' and PAT *ʒ́ǝ-nǝ 'winter', and changed into *(a)ʒ́V by analogy. In that case PWC *ʒǝ could be reconstructed (in Ub. both *ǯ and *ʒ yield ʒ), which would be a perfect match for PEC *jămʒĂ.
Abdokov (1983, 99-100) compares the EC forms with PAK *č:apǝ 'hoar-frost', which seems much less probable (for phonetic reasons).