Re: Putting on my pedant hat...
Originally posted by nephtu
"Knighthood" itself, went through several rounds of re-interpretation, including the early crusading knight, the religious orders like the hospitallers & templars, ideals of Domnei & courtly love, the chivalric romances and so forth, leading up to someone like Sir Galahad in Malory's Morte de Arthur who is probably the prime example from medieval literature for the Paladin as we see them in RPGs.
An excellent summation. I would only add that some orders of knighthood were created strictly in counter to the semi-sacred character of knighthood, which was seen in certain quarters as an attempt by the RCC to encroach on royal privileges.
The book I was thinking about, above, is Maurice Keen's Chivalry, available from Yale Press, and well worth it for its annotated, thorough research and articulateness.

He begins the work by noting the sources of notions of chivalry (which subsequently fed into our ideas of paladinship). The Libre del Ordre de Cavayleria of Ramon Lull (latter part of the 13th century), for example, is described at length, ending with the ideals of knighthood: "He will be a man courteous and nobly spoken, well clad, one who holds open house within the limits of his means. Loyalty and truth, hardiness, largesse and humility will be the principal qualities that we ought to expect in him," and again, later, "Courtesy, loyalty, hardiness, largesse, franchise." Lull himself was a likely catalyst for the whole paladin mythos, being a wealthy, philandering nobleman of some attainment who Got Religion. he developed an elaborate, mystical concept of the universe (which would have gotten him burnt at the stake three hundred years, later), and decided that his mission in life should be to personally convert every follower of Islam to Christianity.

He saw knighthood from the perspective of what it was, and tried to make it into something else, again.
Another influential author of the subject of chivalry was Geoffrey de Charny. His battlefield knighthood credentials place him at the right hand of the French monarchs. He was a member of the knightly and new Order of the Star, created by the French in opposition to Edward III's Order of the Garter, and was appointed bearer of the French king's royal standard, the Oriflamme of St. Denis. He died guarding it at the battle of Poitiers in 1356--talk about romantic.
De Charny wrote three texts on chivalry. They focus on the entire structure of knighhood as a class and an attainment. Keen notes one essential distinction with Lull, whom he says de Charny obviously read: "He is indeed concerned with the tinernal world, as we have seen, but the indices of chivalrous achievement that he suggests are external acts and the repute that has attached to them. In this way his book offers a kind of identikit picture which will assist us in recognizing one who has achieved great things in chivalry by the pattern of his experience and its range, without having to probe for subjective reactions which are unverifiable. He will be a man who has been at jousts and tournaments and at war in other lands beside his own, who has served his lord in arms and has crossed the sea in quest of adventures and fame."
Between the two--Lull on the innate qualities, de Charny on the external actions--we have a pretty good measure of what became the concept of knighthood at its height in the early Renaissance of the 15th century, and the paladin-like qualities in modern AD&D. We can see both sides, Lull and de Charny, in Keldorn, who is first found questing and battling evil, and who later bores everybody with his moral sententiousness.

By contrast, Anomen knows how to fight and wishes to quest, but he lacks the Lullesque, inner qualities of the paladin when you first him.