Where does “kupność” come from?

kupność (Polish) comes from Polish kupny, from Old Polish -ny, from Proto-Slavic -ьnъ — -ish, -ic, -al, -ed; From adjectives.

Ancestry of “kupność”, step by step

StepLanguageWordMeaning
1Polishkupnybought, shop-bought, venal
2Old Polish-nyforms adjectives
3Proto-Slavic-ьnъ-ish, -ic, -al, -ed; From adjectives
Every word from Proto-Slavic -ьnъ →Every word from Old Polish -ny →Every word from Polish kupny →