Where does “osmina” come from?

osmina (Czech) comes from Czech osm, from Old Czech osm, from Proto-Slavic osmь, from Proto-Balto-Slavic aśmas, from Proto-Indo-European oḱtṓwos, from Proto-Indo-European oḱtṓw, from Proto-Indo-European aḱ- — sharp, pointed; sharp, pointed, edgy; sharp,...

osmina (Czech): eighth