PCS

*ḳšw - to be harsh (Kogan 2015: 192)

Cf. perhaps Tgr. ḳäššä ‘to dry up (corn in the sun); to bear no fruit’

Ugaritic
ḳš - oppressor (DUL 717)
Hapax legomenon in 1.16 vi 47‒48: l tdy « ṯ » ḳšm ˁl dl ‘You have not expelled the oppressors from the poor.’
Hebrew
ḳšy - to be heavy, hard (HALOT 1152)
Syriac
ḳšy - to be heavy, hard (LSyr. 703, SL 1418)
Arabic
qsw - to be harsh, cruel (Lane 2988)
Mehri
ḳōsi - cruel (ML 238)
a borrowing from Arabic