Where does “Іллінці” come from?

Іллінці (Ukrainian) comes from Ukrainian Ільїн, from Ukrainian -ї́н, from Old East Slavic -инъ, from Proto-Slavic -inъ, from Proto-Indo-European -iHnos, from Proto-Indo-European -no- — adjectival suffix.

Ancestry of “Іллінці”, step by step

StepLanguageWordMeaning
1UkrainianІльїн—
2Ukrainian-ї́н—
3Old East Slavic-инъ—
4Proto-Slavic-inъ-ine; Creates singulatives, mostly with...
5Proto-Indo-European-iHnosCreates adjectives of materials
6Proto-Indo-European-no-adjectival suffix
Every word from Proto-Indo-European -no- →Every word from Proto-Indo-European -iHnos →Every word from Proto-Slavic -inъ →