PNWS

*ḥšk - to be dark (Kogan 2015:237)

hypothetical Arabic cognates (ḥsk - ‘to bear rancor’; suḥkūk - ‘black’) are rather remote both formally or semantically

Hebrew
ḥšk - to be dark (HALOT 361)
Syriac
ḥšk - to be darkened, to be eclipsed (LSyr. 262, SL 501)