Where does “acht” come from?

acht (Old Czech) comes from Middle High German āhte, from Old High German ahtô, from Proto-Germanic ahtō, from Proto-Germanic ahtōu, from Proto-Indo-European oḱtṓw, from Proto-Indo-European aḱ- — sharp, pointed; sharp, pointed, edgy; sharp,...

acht (Old Czech): anathema