Where does “sinä” come from?

sinä (Veps) comes from Proto-Finnic cinä, from Proto-Uralic tinä — you, thou.

sinä (Veps): you

Definitions

Step	Language	Word	Meaning
1	Proto-Finnic	cinä	you
2	Proto-Uralic	tinä	you, thou

sinä — Etymology, Origin & Word History | Etymology Explorer