Semitic Etymological Database
Perhaps distantly related to Proto-MSA *lsy ‘to rain’ (Kogan 2015:104).
Probably a combination of the ingressive n- and the biconsonantal verbal root mŝ.
Derived words: napalsuḫtu, napalsaḫtu, napalsiḫtu ‘footstool, stooľ (CAD N₁ 271, AHw. 733). Ugr. prsḥ ‘to collapse’ comes remarkably close to the Akkadian verb in both form and meaning. Also cf. Tna. färšäḥe ‘to destroy, to collapse; to knock down’, Ar. farsaḫa ‘to decrease (of cold)’.