Where does “sois” come from?

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

sois (Asturian): second-person plural present indicative of ser

Definitions

second-person plural present indicative of ser

Ancestry of “sois”, step by step

Step	Language	Word	Meaning
1	Asturian	ser	to be; being
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 →