shotgun (n.) Look up shotgun at
1821, American English, from shot (n.) in the sense of "lead in small pellets" (1770) + gun (n.). As distinguished from a rifle, which fires bullets. Shotgun wedding first attested 1903, American English. To ride shotgun is 1963, from custom of having an armed man beside the driver on the stagecoach in Old West movies to ward off trouble.