The Proto-Turkic word *düĺ-ün-
Word *düĺ-ün-
Meaning to think, understand
Synonyms *ö̅(j)-, *seŕ-

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