Where does “Siina” come from?

Siina (Finnish) comes from Russian Зи́на, from Russian Зинаи́да, from Ancient Greek Ζηναΐς.

Ancestry of “Siina”, step by step

Step	Language	Word	Meaning
1	Russian	Зи́на	—
2	Russian	Зинаи́да	—
3	Ancient Greek	Ζηναΐς	—

Siina — Etymology, Origin & Word History | Etymology Explorer