PWS

*paḫiḏ- - hip, thigh (SED I No. 211, Kogan 2011: 225)

On the semantic shift ‘hip, thigh’ > ‘tribal union’ see Kogan-Militarev 2003 295-296.

Hebrew
paḥad - thigh, haunch (HALOT 923)

Probably related. There is a tradition of translating this word as ‘testiculus’ (a discussion supporting this opinion see in [Pope 272]).

Deir Alla
phz - tribal union (DNWSI 905)
Palmyrean
pḥz - tribal union (DNWSI 905)
St. abs.: pḥz, St. constr.: pḥd.
Jewish Babylonian Aramaic
paḥdīn - testiculi (Jastrow 1151)

(pl.). A similar shift of meaning see in Akk.paḫallu ‘thigh’ vs. ‘penis’ in other Sem. (cf. *paḫiḏ- - hip, thigh No. 210) and in Akk. birku ‘knee; lap; male and female sexual parts’ [CAD b 255]. 

Syriac
puḥdā - thigh, buttocks (LSyr. 562, SL 1161)
Arabic
faḫiḏ- - thigh; the smallest subdivision of a tribe (Lane 2349, BK 2 552)
Also faḫḏ-, fiḫḏ-.
Sabaic
fḫḏ - thigh (SD 43)
Qatabanian
fḫḏ - clan, family, sub-tribe (LIQ 129)
Mehri
əfḫāḏ - flesh and bone of upper leg from knee to hip (ML 110)
fəḫə́ḏət ‘tribe’ (ML 110)
Jibbali
faḫḏ - flesh and bone of upper leg from knee to hip (JL 67)
fḫə́ḏət ‘tribe’ (JL 67)
Harsusi
efḫāḏ - thigh (HL 37)
Soqotri
fâḥid - people (LS 335)

An areal Arabian semantic evolution?