Many people assume “AR” stands for “assault rifle” which is a logical assumption since AR 15s are popularly classed as assault rifles (although true “assault rifles” offer selective single shot or automatic fire) but it’s just a coincidence. “AR” stands for “ArmaLite” which is the name of the company where the AR 15’s inventor Eugene Stoner invented the rifle in 1955. When the military adopted the fully-automatic version of the rifle they named in the M16. The semiautomatic models sold on the civilian market are known to many as “ARs.”