Where does “třeťák” come from?
třeťák (Czech) comes from Czech třetí, from Proto-Slavic tretь, from Proto-Balto-Slavic tretias, from Proto-Balto-Slavic tirtias, from Proto-Indo-European tr̥tyos, from Proto-Indo-European *tréyes.
třeťák (Czech): a third grader
Ancestry of “třeťák”, step by step