Comments:EAS 91, KW 118, Poppe 55, VEWT 38, АПиПЯЯ 292, Цинциус 1972a, 29-31, Дыбо 6. The root is (like most other kinship terms) a "nursery word", but very well attested in all branches, so - despite Doerfer TMN 1, 190-191 - all forms cannot be explained as borrowings (although some later interactions were of course possible, e.g. Mong. egeče may - because of its irregular -g- and meaning coinciding with Turkic - be a later Turkic loanword).
