Where does “jeśm” come from?

jeśm (Old Polish) comes from Proto-Slavic *esmь, from Proto-Balto-Slavic esmi, from Proto-Indo-European h₁ésmi, from Proto-Indo-European h₁ēs- — to be.

Ancestry of “jeśm”, step by step

StepLanguageWordMeaning
1Proto-Slavic*esmь(I am)
2Proto-Balto-Slavicesmifirst-person singular present of *bū́ˀtei
3Proto-Indo-Europeanh₁ésmifirst-person singular present indicative of...
4Proto-Indo-Europeanh₁ēs-to be
Every word from Proto-Indo-European h₁ēs- →Every word from Proto-Indo-European h₁ésmi →Every word from Proto-Balto-Slavic esmi →