PCS
*waṣil- - joint, articulation (of the humerus)
(SED I No. 289)
As a nominal root with anatomic meaning, C. Sem. only.
Traditionally regarded (for example, in HALOT 82) as deverbal of Sem. *ˀ/wṣl ; the connection is quite plausible. For this verbal root see DRS 593.