Where does “-ник” come from?

-ник (Bulgarian) comes from Proto-Slavic -ьnikъ, from Proto-Slavic -ikъ — *nožь → *nožikъ; *větrъ → *větrikъ; *listъ →...

-ник (Bulgarian): From base concept nouns, forms agent nouns who execute, embark on or embody the referred concept