Where does “Melnychuk” come from?

Melnychuk (English) comes from Ukrainian Мельничук, from Ukrainian -у́к, from Proto-Slavic *-ukъ.

Ancestry of “Melnychuk”, step by step

StepLanguageWordMeaning
1UkrainianМельничук—
2Ukrainian-у́кAdded to an often diminutive stem to form a patronymic or matronymic surname
3Proto-Slavic*-ukъ—
Every word from Proto-Slavic *-ukъ →Every word from Ukrainian -у́к →Every word from Ukrainian Мельничук →