Arabic

fsḫ - to dislocate, to remove from its place, to separate, to disperse; to be weak in intellect and in body (BK 2 592, Lane 2395)

Alternatively, may go back to PWS *pṣḥ ‘to smash, to grind’ or PWS *pšḫ ‘to break off, to separate’.

PS
*psḥ/ḫ - to be lame; have a dislocated limb (SED I No. 54ᵥ; HALOT 947)