Jaw

PIE *ĝenu-
Gloss: ‘chin, jaw(-bone)’ (item 17 in Bjørn 2017)

Attestations:
Toch. A śanwe-ṃ (du.); OIr. gin; Goth. kinnus; Gr. γένυς; Phr. α-ζήν ‘beard’; Ved. hanu-, Av. zanva (acc. du.).

Notes: The problematic velar reflexes in Indo-Iranian formally require *ĝh, which has been proposed as “Homoionymenflucht”, i.e. dissimilation from *ĝonu- ‘knee’ (item 20) with which it was colliding in the Indo-Iranian vowel collapse of *e and *o to a (Mayrhofer 1996: 801f.), although *-o- in ‘knee’ is lengthened due to the effects of Brugmann’s Law.

External comparanda:
NE Caucasian: *č̣ănV ‘chin’ (NCED s.v.)

Discussion:
S. Starostin makes no distinction as to the stage of transfer (2009: 85), but the palatal development of an inherited plain velar in front of a front vowel is a strong argument in favor of a dialectal loan from a stage of Indo-Iranian into NE  Caucasian (Dolgopolsky 1987: 19), and, if the vowel reconstructed by Nikolayev & Starostin is to be preferred to Dolgopolsky’s cover symbol, the vocalism helps substantiate a loan with the hallmark traits of Indo-Iranian (§ 1.3.2.13).