The word cavalry is derived from the French word cavalerie which means horse. Historically the term cavalry has been used to represent troops mounted on horseback. After the invention of battle tanks and the decline of usage of horses in army the term started representing tanks regiments. Which army first stated to call its tanks regiments as Cavalry? And when did this happen? Why are tank regiments called cavalry but not other mechanized regiments (e.g. mechanized infantry or artillery)?
Several reasons. First and foremost, they perform the same role on the battlefield, providing a fast moving spearhead.