Where does “искренно” come from?

искренно (Russian) comes from Russian и́скренний, from Proto-Slavic *jьzkrьňь — close.

Ancestry of “искренно”, step by step

StepLanguageWordMeaning
1Russianи́скреннийsincere
2Proto-Slavic*jьzkrьňьclose
Every word from Proto-Slavic *jьzkrьňь →Every word from Russian и́скренний →