Where does “вареннячко” come from?

вареннячко (Ukrainian) comes from Ukrainian -чко, from Ukrainian -це́, from Ukrainian -ко, from Proto-Slavic -ьko.

Ancestry of “вареннячко”, step by step

StepLanguageWordMeaning
1Ukrainian-чкоy, -ling forming diminutive nouns, usually endearing
2Ukrainian-це́y, -ling
3Ukrainian-коCreates diminutives of normally neuter nouns and adverbs, normally having a colloquial register
4Proto-Slavic-ьko—
Every word from Proto-Slavic -ьko →Every word from Ukrainian -ко →Every word from Ukrainian -це́ →