The term 'Blue Moon of Baseball' refers to a rare occurrence in Major League Baseball when a team plays two games on the same day. The term was coined by broadcaster Red Barber in 1926, and is derived from the phrase 'once in a blue moon, ' which means something that happens very rarely. The crossword solution for this term is ODOM, which stands for 'doubleheader, ' another term for two games played on the same day.