From the old French word for knighthood, "chevalerie", the art of being a chevalier (a knight or horseman).
This was
originally a system by which mounted warriors were to act, but while service to their people is touched upon
the general goal of medieval knights was not saving many a damsel in distress, devotion to God, or enforcing justice; most knights defined chivalry as warfare and obtaining fame and fortune in the name of their king(s) and without any display of cowardice in battle.
In a sense, it's hardly different from joining the military for the benefits that it offers, including the money that pours in from the business of war. Chivalry was
basically a boy's culture: fighting other men, riding horses, power and profit and the ability to exploit that power.
The modern notion of chivalry as courtesy to women has tenuous links to chivalry as it was
originally conceived. Perhaps courtly love (coined in 1883 to describe the worship of a married noblewoman by a lowly troubadour or knight and his vow to do great deeds in her honor) influenced this notion, but courtly love is, for all intents and purposes, adultery (very dangerous to both participants) and to what extent that courtly love was ever practiced remains unknown.
Chivalry, for the most part, was the opposite of the Geneva Convention; it was all about making a profit on war. The image of an honorable knight saving a fair maiden from a dragon is not much more than sheer fantasy, and most of it seems to stem from the
Victorian era; the Victorians, in the midst of the
Industrial Revolution, looked at the Middle Ages through rose colored glasses as an idyllic place of pre-industrial innocence, projecting their own ideals of men and women onto the knight and the damsel in distress. A real
knight in shining armor was actually more like a trained assassin and the local rapist rolled into one and the damsel in distress, a helpless shrinking violet, never really existed.