“Nay,” said Sir Lancelot “…for once
shamed may never be recovered.”
French for the Ill-Made Knight, though it may be translated as the Ugly Knight, the Knight Who Has Done Wrong, the Ill-Starred Knight, or the Knight with a Curse on Him. Lancelot took this name in reference to his disfigured appearance as well as his sinful nature. The sins of Lancelot included the cuckolding of his best friend King Arthur and his intense pride in himself which he could not help.
Lancelot actually began using this name after faking his own death in order to live peacefully with Elaine, the mother of his bastard child Galahad. If the whereabouts of Lancelot had been known there would be a great cry for him to return to the Court of the Round Table. After many years living faithfully with Elaine and Galahad, Lancelot returned to court under this pseudonym.
Lancelot’s sins prevented him from holding the title as the worlds greatest knight, an honor then held by his virgin son Galahad. The situation is punctuated in the only battle fought between father and son when Galahad unseats Lancelot and is hailed by a mysterious woman as the greatest knight in the world. This was also the reason for which Lancelot was never to fulfill his quest for the grail, as only the greatest knight in the world (without sin) could lay eyes upon it (a privilege again held only by Galahad).