Short answers, pulled from the story.
The name Orestes derives from ancient words meaning mountain and to stand, combining to mean stands on a mountain. This linguistic root connects the figure to the House of Atreus in Greek mythology.
Harry Thurston Peck recorded this definition in his Harpers Dictionary of Classical Antiquities published on the 1st of January 1898. Robert Graves noted that obscure threads of much older works remain within these myths.
Seven years passed before the young man returned from Athens after his father Agamemnon was murdered by Aegisthus. He avenged his father's death by killing both Aegisthus and Clytemnestra upon his return.
Athena received him on the Acropolis of Athens to arrange a formal trial with twelve judges including herself. The votes counted evenly forcing an acquittal under stipulated rules which converted the Erinyes into Eumenides offering wisdom and counsel instead of punishment.
Giangualberto Barlocchi wrote the Roman libretto used for this production in 1723. Darius Milhaud composed L'Orestie d'Eschyle as a French-language opera between the 1st of January 1913 and the 31st of December 1923.
Lichas discovered the body measuring seven cubits long which equals approximately 311.5 centimeters if one cubit is 44.5 centimeters. Ancient observers concluded Orestes must have been a giant based on these dimensions found in caves near Megalopolis.