|John Wayne riding shotgun in Stagecoach|
The usage has its roots in a bygone era of the American West when stagecoaches were common. At least in the retelling of American history through films and television, we learned that back in the 1880s the seat next to the driver on top was given to someone with a gun.
Though shotguns offered the chance to hit one or more attackers more easily from a bouncing seat, we also have seen on the screen men with rifles and pistols riding shotgun. The term became a generic way of describing the seat and the duty.
The phrase appears in the 1939 John Ford film Stagecoach starring John Wayne who declares that “I’m gonna ride shotgun.” Randolph Scott starred in a 1954 film titled Riding Shotgun.
Though we hope no one today who calls shotgun when getting into a car is carrying a weapon, the term has survived in slang usage. In the 21st century, riding shotgun might require monitoring the GPS and answering phone calls and text messages for the driver, which are jobs that might actually save the driver's life.