Currently airing its fifth and final season, “Yellowstone” follows the Dutton family, owners of the largest ranch in Montana, including patriarch John (Kevin Costner), who was also the governor, and his adult children Kayce (Luke Grimes), Jamie (Wes Bentley), Beth (Kelly Reilly) and Beth’s husband, Rip (Cole Hauser).

The tradition is of Native American heritage, and those who think Mo told Kayce to do it are almost certainly right. Per the University of Nebraska's Encyclopedia of the High Plains, counting coup is a high honor for warriors. It means to get close enough to a combatant to strike him by hand and is thought be a great sign of courage.