“Proto-MSA *ŝiwāṭ- ‘fire’ has been correctly identified by Leslau with Arb. šawṭ- ‘heat’ (Lane 1619), Syr. sāṭ ‘combustus est’ (LSyr. 463). There is no trace of PS *ˀiš(-āt)- ‘fire’ in MSA.” (Kogan 2015:539)
The origin is uncertain, but Leslau may be correct to relate it to PS *hlk ‘to go.’ (Kogan 2015:573)
With no evident Semitic etymology (for the rather sparse Akkadian comparanda see Kogan 2015:539).
The origin is unknown (Kogan 2015:574)
Is likely related to Tgr. šəfər ‘manure, dung’ (WTS 230), but further possible cognates are rather uncertain (SED I No. 282). (Kogan 2015:575)
In a personal communication, M. Krebernik suggests an interesting possibility of comparing proto-MSA *ṯḥr ‘to wound’ with Sargonic Akkadian šaˀāru (iš₁₁-ar) ‘to conquer, to win, to destroy’ (CAD Š₁ 2). This etymology provides a far better balance of semantic and phonological/orthographic features than the more traditional comparisons with either PS *ṯγr ‘to break’ or Arabic ṯˀr ‘to take blood-revenge.’ (Kogan 2015:575, fn. 1493)