Where does “скорлупка” come from?

скорлупка (Russian) comes from Russian скорлупа, from Old East Slavic скорлупа, from Proto-Slavic skorupa, from Proto-Slavic skora, from Proto-Indo-European (s)ḱer- — dung, manure, filth; manure, dung, filth.

Ancestry of “скорлупка”, step by step

StepLanguageWordMeaning
1Russianскорлупаshell (of an egg or animal), hull
2Old East Slavicскорлупа—
3Proto-Slavicskorupacrust?, shell?
4Proto-Slavicskorabast, skin
5Proto-Indo-European(s)ḱer-dung, manure, filth; manure, dung, filth
Every word from Proto-Indo-European (s)ḱer- →Every word from Proto-Slavic skora →Every word from Proto-Slavic skorupa →