Where does “истинность” come from?

истинность (Russian) comes from Russian и́стинный, from Old East Slavic истиньнъ, from Old East Slavic -ьнъ, from Proto-Slavic -ьnъ — -ish, -ic, -al, -ed; From adjectives.

истинность (Russian): fact, sooth, truth, verity, validity

Definitions

  1. fact, sooth, truth, verity, validity

Ancestry of “истинность”, step by step

StepLanguageWordMeaning
1Russianи́стинныйveritable, true
2Old East Slavicистиньнъtrue
3Old East Slavic-ьнъish, -ic, -al, -ed
4Proto-Slavic-ьnъ-ish, -ic, -al, -ed; From adjectives
Every word from Proto-Slavic -ьnъ →Every word from Old East Slavic -ьнъ →Every word from Old East Slavic истиньнъ →