Where does “essergli” come from?

essergli (Italian) comes from Italian essere, from Late Latin essere, from Latin sūm, from Proto-Italic ezom, from Proto-Indo-European h₁ésmi, from Proto-Indo-European h₁ēs- — to be.

Ancestry of “essergli”, step by step

Step	Language	Word	Meaning
1	Italian	essere	Used as a to be
2	Late Latin	essere	—
3	Latin	sūm	to be, exist
4	Proto-Italic	ezom	to be
5	Proto-Indo-European	h₁ésmi	first-person singular present indicative of...
6	Proto-Indo-European	h₁ēs-	to be

Every word from Proto-Indo-European h₁ēs- →Every word from Proto-Indo-European h₁ésmi →Every word from Proto-Italic ezom →