Arabic

ˁaṣaṣ-, ˁuṣuṣ-, ˁuṣˁūṣ- - caudal bone of the tail (BK 2 272, Lane 2057)

Related with reduplication.

PWS
*ˁaṣay- - coccyx, backbone (SED I No. 23; Kogan 2011: 218)
Vocalism tentative.