Where does “sebdmъ” come from?

sebdmъ (Proto-Slavic) comes from Proto-Slavic septmъ, from Proto-Balto-Slavic septmas, from Proto-Indo-European septḿ̥ — seven.

Ancestry of “sebdmъ”, step by step

StepLanguageWordMeaning
1Proto-Slavicseptmъ—
2Proto-Balto-Slavicseptmas—
3Proto-Indo-Europeanseptḿ̥seven
Every word from Proto-Indo-European septḿ̥ →Every word from Proto-Balto-Slavic septmas →Every word from Proto-Slavic septmъ →