köken: Etymology tree Proto-Indo-European *Hrek-der. Proto-Slavic *reťi Proto-Indo-European *-os Proto-Slavic *-ъ Proto-Slavic *rȍkъ Old Polish rok Polish rok Proto-Indo-European *-nós Proto-Balto-Slavic *-inas Proto-Slavic *-ьnъ Old Polish -ny Polish -ny Polish roczny From rok + -ny.