duben.

Inherited from Old Czech duben, from Proto-Slavic *dǫbьnъ. By surface analysis, dub + -en. This term derives from the Czech word for "oak," which is dub. The reason for this connection is that April is the time of year when oak trees typically shed their old leaves and begin to grow new ones. This prominent sign of renewal and the reawakening of nature is why the Czechs associated the month with the oak tree. This naming convention, where month names are derived from natural phenomena or agricultural activities common during that time, is a characteristic of the traditional Slavic calendar, to which Czech belongs. Unlike many other European languages that adopted Latin-based month names, Czech (along with Croatian, Polish, and Ukrainian) has largely retained its original Slavic month names.