The etymology of asperity is "rough." It is adapted from Middle English asprete, which was borrowed from the Anglo-French aspreté, and ultimately derives from the Latin word asper, which means "rough." Not only is asper the source of asperity, but it also underlies the English word exasperate (in fact, you can see asper nestled in the midst of that word). Although it is far less common than asperity and exasperate, the word asper itself is still occasionally used in English—it functions as a synonym of harsh, bitter, and stern.