Where does “Alexej” come from?

Alexej (Slovak) comes from Russian Алексе́й, from Russian Алекси́й, from Ancient Greek Ἀλέξιος, from Ancient Greek -ῐος, from Proto-Indo-European -yós — Creates adjectives from noun or verb stems.

Ancestry of “Alexej”, step by step

StepLanguageWordMeaning
1RussianАлексе́йAlpha (A in the ICAO spelling alphabet)
2RussianАлекси́й—
3Ancient GreekἈλέξιοςhelper, defender
4Ancient Greek-ῐοςbelonging to; of”, “belonging to”, “pertaining to
5Proto-Indo-European-yósCreates adjectives from noun or verb stems
Every word from Proto-Indo-European -yós →Every word from Ancient Greek -ῐος →Every word from Ancient Greek Ἀλέξιος →