The Proto-Turkic word *kāpuk
Word *kāpuk
Meaning bark, shell
Synonyms *kaŕ, *kɨrtɨĺ

Comments
S. A. Starostin, A. V. Dybo, O. A. Mudrak - An Etymological Dictionary of Altaic Languages, 2003, Brill

Other words that might be of interest
*bālɨk ‘fish’