The crossword solution for the term 'Bygone Persian' is MEDE. This is a reference to the Medes, an ancient Iranian people who lived in the western and northwestern regions of modern-day Iran from the 6th century BC until the 7th century AD. They were one of the most powerful nations of their time and were known for their military prowess. The Medes were eventually conquered by the Achaemenid Empire, which was founded by Cyrus the Great in 550 BC.