Etimoloji
Etymology tree Proto-Indo-European *trewd- Proto-Balto-Slavic *tráudas Proto-Slavic *trudъ Proto-Indo-European *-nós Proto-Balto-Slavic *-inas Proto-Slavic *-ьnъ Proto-Slavic *trudьnъ Old Polish trudny Proto-Slavic *-o Old Polish -o Old Polish trudno Polish trudno Inherited from Old Polish trudno. By surface analysis, trudny + -o. Compare Russian тру́дно (trúdno).