↑ "dub" inJiří Rejzek, Český etymologický slovník, Leda, 2015, ISBN 978-80-7335-393-3, page 160.
Etymology
From Proto-Slavic*dǫbъ(“oak”), which has not been explained yet. It could be an innovation appearing because of a taboo (since oak was a sacred tree). There are some attempts to connect it with eg. Proto-Indo-European*dem-(“build”), *dʰeu-bʰ-(“dark”), *dʰeu-b-(“deep”) or *dʰembʰ(“beat”).[1]