Where does “słoniuscko” come from?

słoniuscko (Polish) comes from Polish słońce, from Proto-Slavic sъlnьce, from Proto-Balto-Slavic *súlˀnis, from Proto-Indo-European sóh₂wl̥ — sun.

Ancestry of “słoniuscko”, step by step

StepLanguageWordMeaning
1Polishsłońcesun
2Proto-Slavicsъlnьcesun
3Proto-Balto-Slavic*súlˀnissun
4Proto-Indo-Europeansóh₂wl̥sun
Every word from Proto-Indo-European sóh₂wl̥ →Every word from Proto-Balto-Slavic *súlˀnis →Every word from Proto-Slavic sъlnьce →