Arabic

fakk- - joint connecting the two jaws; part of a mouth comprising both jaws (BK 2 624)

Cf. also fanik- ‘endroit où les deux mâchoires se joignent; endroit de la bouche compris entre la lèvre inférieure et le menton à la naissance de la barbe’ [BK 2 639] (with a secondary -n-?).

PWS
*pakk- - jaw, joint of the jaw (SED I No. 212)
Rather scarce but reliable attestation. -n- in one of the Arb. forms may imply Sem. *pank- > *pakk-. Cf. a variant root *pagg- ‘jaw’: Hbr. pB. pag (Jastrow 1132); Jud. pagga (ibid.), Syr. pagga (LSyr. 555).