The quality or state of being rude and impolite; lack of courtesy or respect in manner or behavior.
From dis- (opposite of) + courtesy + -ness (quality). Courtesy comes from Old French 'cortoisie,' related to 'court,' meaning behavior befitting a court. The prefix dis- negates it, and -ness makes it a noun for the abstract quality.
Medieval courts invented the concept of 'courtesy' as a code of refined behavior, so discourteousness literally means falling short of what a noble court would expect—but nowadays it just means being rude to anyone, not just nobility!
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