asperity

Asperity has had a rough history. It came to Modern English through Middle English (where it was spelled "asprete") by way of the Anglo-French ("asprete"), 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, too - it functions as a synonym of "harsh," "bitter," or "stern."