Where does “Костюк” come from?

Костюк (Ukrainian) comes from Russian -юк, from Proto-Slavic *-ukъ.

Ancestry of “Костюк”, step by step

StepLanguageWordMeaning
1Russian-юк—
2Proto-Slavic*-ukъ—
Every word from Proto-Slavic *-ukъ →Every word from Russian -юк →