This painting is a small piece, probably intended for a use in a private chapel rather than a large church. Louis I, Duke of Orléans, became regent of France, when his older brother Charles VI went insane, and then Duke of Orleans was assassinated by his cousin & co-regent John the Fearless, Duke of Burgundy. His murderer John’s courage against Ottoman forces in the Battle of Nicopolis (1396) earned him his nickname, and his bullheaded vanity helped ensure his side was utterly routed. You can read all about it in Barbara Tuchman’s A Distant Mirror: The Calamitous 14th Century.
The garden at Gethsemane, a place whose name literally means oil press, is located on a slope of the Mount of Olives just across the Kidron Valley from Jerusalem. A garden of ancient olive trees stands there to this day. Jesus frequently went to Gethsemane with His disciples to pray (John 18:2).