||From Proto-Celtic *genu- 'jaw' < PIE: *g̑enu- 'jaw' (IEW 381).
The singular of this word is reflected in OIr. gin u m. 'mouth' and in the Brittonic words for 'cheek', MW gen f.'cheek', OBret. gen gl. maxilla, MBret. guen, MoBret. gen f. 'cheek'.
The Breton word for 'mouth' is based on the plural Proto-Celtic *genou̯es.