Where does “prodlužka” come from?

prodlužka (Czech) comes from Czech prodloužit, from Czech dlouhý, from Old Czech dlúhý, from Proto-Slavic dь̀lgъ, from Proto-Balto-Slavic dílˀgas, from Proto-Indo-European dl̥h₁gʰós — long.

Ancestry of “prodlužka”, step by step

StepLanguageWordMeaning
1Czechprodloužitto prolong; to lengthen
2Czechdlouhýlong; tall
3Old Czechdlúhýlong
4Proto-Slavicdь̀lgъlong
5Proto-Balto-Slavicdílˀgaslong
6Proto-Indo-Europeandl̥h₁gʰóslong
Every word from Proto-Indo-European dl̥h₁gʰós →Every word from Proto-Balto-Slavic dílˀgas →Every word from Proto-Slavic dь̀lgъ →