Quick answer
Orestes is a boy name meaning "of the mountains".
Pronunciation: Classical Greek /o.res.tɛːs/; English /ɔ.ˈɹɛs.tiːz/.
Meaning and history
The name means "of the mountains", derived from Greek ὄρος ( oros ) meaning "mountain" and ἵστημι ( histemi ) meaning "to stand". In Greek myth he was the son of Agamemnon and Clytemnestra. He killed his mother and her lover Aegisthus after they killed his father.
Notes and context
Usage: greek mythology | Ancient Greek: Ὀρέστης