mid-14c., nobilite, "honor, renown; majesty, grandeur;" late 14c., "quality of being excellent or rare," from Old French nobilite "high rank; dignity, grace; great deed" (12c., Modern French nobilité), and directly from Latin nobilitatem (nominative nobilitas) "celebrity, fame; high birth; excellence, superiority; the nobles," from nobilis "well-known, prominent" (see noble (adj.)).
Meaning "quality of being of noble rank or birth; social or political preeminence, usually accompanied by hereditary privilege" is attested from late 14c.; sense of "the noble class collectively" is from late 14c. Sense of "dignity of mind, elevation of the soul, loftiness of tone" is from 1590s.
In application to things nobleness is rather more appropriate than nobility, as the nobleness of architecture or one's English, while nobility is more likely to be applied to persons and their belongings, as nobility of character or of rank; but this distinction is no more than a tendency as yet. [Century Dictionary, 1895]
c. 1300, "body or host of knights; knighthood in the feudal social system; bravery in war, warfare as an art," from Old French chevalerie "knighthood, chivalry, nobility, cavalry, art of war," from chevaler "knight," from Medieval Latin caballarius "horseman," from Latin caballus "nag, pack-horse" (see cavalier).
From late 14c. as "the nobility as one of the estates of the realm," also as the word for an ethical code emphasizing honor, valor, generosity and courtly manners. Modern use for "social and moral code of medieval feudalism" probably is an 18c. historical revival.