Where does “ruakku” come from?

ruakku (Karelian) comes from Russian ра́к, from Proto-Slavic rakъ, from Proto-Balto-Slavic rṓˀkas, from Proto-Indo-European wreh₃kʷos — looking backwards.

Ancestry of “ruakku”, step by step

StepLanguageWordMeaning
1Russianра́к—
2Proto-Slavicrakъcrayfish
3Proto-Balto-Slavicrṓˀkas—
4Proto-Indo-Europeanwreh₃kʷoslooking backwards
Every word from Proto-Indo-European wreh₃kʷos →Every word from Proto-Balto-Slavic rṓˀkas →Every word from Proto-Slavic rakъ →