courtesy (n.)

c. 1200, curteisie, "courtly ideals; chivalry, chivalrous conduct; elegance of manners, politeness," also "a courteous act, act of civility or respect," from Old French curteisie, cortoisie "courtliness, noble sentiments; courteousness; generosity" (Modern French courtoisie), from curteis "courteous" (see courteous).

From c. 1300 as "good will, kindness," also "a reward, a gift;" mid-14c. as "refinement, gentlemanly conduct." A specialized sense of curteisie is the source of English curtsy. A courtesy title (1829) is one to which one has no valid claim but which is assumed or given by popular consent. Courtesy call "visit made for the sake of politeness" is by 1898.