Where does “частенько” come from?

частенько (Ukrainian) comes from Ukrainian ча́сто, from Ukrainian ча́стий, from Proto-Slavic čęstъ, from Proto-Balto-Slavic *kimśtas.

Ancestry of “частенько”, step by step

StepLanguageWordMeaning
1Ukrainianча́стоfrequently, often
2Ukrainianча́стийfrequent
3Proto-Slavicčęstъfrequent, dense
4Proto-Balto-Slavic*kimśtas—
Every word from Proto-Balto-Slavic *kimśtas →Every word from Proto-Slavic čęstъ →Every word from Ukrainian ча́стий →