Well it is hard to determine really, but it seems that our notion of chivalry comes from the medieval courtly love, where the young and aspiring knight would court his chosen lady, apparently somewhat free of intereference of their parents (relative mind you).
That was a totally new concept and something that was relegated to the higher classes (the knights) who could aford to do poetry, play music, dance, or if need be win tournaments.

That might be where our romantic vision of the knight on the white horse comes from, rather than them actually rescuing the damsel in distress ffrom and evil baron or a dragon.