Where does “Serguei” come from?

Serguei (Portuguese) comes from Russian Серге́й, from Ancient Greek Σέργιος, from Latin Sergius.

Ancestry of “Serguei”, step by step

Step	Language	Word	Meaning
1	Russian	Серге́й	Sergius
2	Ancient Greek	Σέργιος	—
3	Latin	Sergius	—

Serguei — Etymology, Origin & Word History | Etymology Explorer