Arabic

kumuddat- - penis (BK 2 929)

Likely a semantic shift; for a similar shift, cf. Ugr. yd, Hbr. yād ‘hand’ and ‘penis’ [HALOT 387]; and Arm. Jud. ˀammətā ‘cubit; membrum virile’ [Jastrow 79] (see *ˀamm­-at-­ ‘elbow, forearm’, No. 6).

PS
*kVm(V)d- - forearm, cubit (SED I No. 144)
A phonetic diversity throughout Sem. can be explained by (1) lower compatibility of a voiced and voiceless stop in Hbr. and Arm., and (2) change of *­m­ > ­n­ in contact with ­-d (for a similar phonetic evolution cf. *p/ban/md(­at)­ ‘back, podex’, No. 216).