This conventional reconstruction does not pretend to describe with full adequacy all the extant cognates. Problems connected with the reconstruction of the PS term for “root” are extensively discussed in Faber 1984:213‒219. (Kogan 2015:42, note 99)
Akkadian
šuršu - root, base, foundation
(CAD Š₃ 363, AHw. 1286)
Note 102: “One has to agree with Leslau (CDG 533) who believes that Arb. širš- ‘root’ (Dozy I 745) “does not give the impression of being an original Arabic root.” “