Where does “jis” come from?

jis (Proto-Baltic) comes from Proto-Indo-European éy, from Proto-Indo-European h₁e-.

Ancestry of “jis”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	éy	the; demonstrative pronoun; this one, he
2	Proto-Indo-European	h₁e-	—

jis — Etymology, Origin & Word History | Etymology Explorer