How to say "fist" in Arabic

Qabḍa 'fist, grip' sits on ق-ب-ض 'to seize, grasp' — and ض is the regular partner of Hebrew צ, which would give ק-ב-צ, the root behind קיבוץ and קבוצה, 'gathering, collective'. The link isn't certain, but it's a tempting one under the regular sound correspondences: grasping in Arabic, gathering in Hebrew — fingers closing around something re-imagined as people closing ranks together.