Orestes \o-res-tes, or(e)-stes\ as a boy's name is of Greek origin, and the meaning of Orestes is "mountain". Greek mythology: Orestes was the son of Agamemnon, king of Argos and one of the Greek conquerors of Troy. Orestes was ordered by the god Apollo to avenge his father's death, but in so doing he committed the crime of matricide. Upon the king's return from the Trojan War, he was murdered by his wife, Clytemnestra, and her lover, Aegisthus. Orestes appears in eight of the classic Greek tragedies.