In the aristocratic society in which Lancelot lived, one's identity was almost entirely dependent on one's name. This is why Lancelot's feat of accepting a ride in a cart is so devastating. To ride in the cart was an act of shame, as the cart was used to transport criminals. Throughout the story, there are many instances where characters, such as Gawain, insist that death is preferable to the shame of riding in a cart. Because of his actions, for much of the story, Lancelot is known only to us as "the Knight of the Cart." The news of Lancelot's ride in the cart spreads quickly and he isoften judged or even mocked for his actions. While no one ever addresses him as "the Knight of the Cart," it essentially becomes his name. The narrator is predominantly the one who refers to Lancelot as that shameful title, although when Lancelot arrives at the meadow where there are many people playing games he is almost immediately recognized.
See See It's the knight
Who rode in the cart " (ll. 1670-1673)
Lancelot is also recognized as the Knight of the Cart later in the story by an arrogant knight thirsty for a fight. He taunts Lancelot by asking him if he'd thought everyone had forgotten about his bout with the cart and calls him shameless and foolish. Clearly, Lancelot's decision to accept a ride in the cart tarnished his reputation. However, this decision of Lancelot's gives some insight into his true identity.
Lancelot's identity is indeed that of a knight. He shows many of the qualities of the stereotypical knight throughout the text. He is generous (after the girl releases him from Meleagant's tower, he refuses the gift horse that they want to give to him and he insists that the gift be given to the two men who rode with him), courageous (his many battles), determined (he rides in the cart in order to get to Guinevere), and loyal (he returns to his prison because he gave his captor his word that he would). However, the power of Love makes him somewhat unstable. He is too trusting and a bit naive. After he leaves the Queen, he accepts a ride from a Dwarf who ends up bringing him to Meleagant. He is also so affected by Love that is drives him to a suicide attempt and also, it almost causes him to faint on two separate occasions.
Lancelot's name changes over the course of the story. How the narrator refers to Lancelot is telling of how his character is being viewed at the time. When the story begins, he is referred to only as "the knight." We do not know much about him; only that he seemed to be in a hurry to get somewhere. Next, he is referred to as "the Knight of the Cart" after he accepts that shameful ride. For many lines, this act is the only one we have to judge Lancelot by. At line 735, the narrator beings to use the phrase, "our knight." This is after Lancelot has a glimpse of the Queen, but cannot reach her. He is left shaken and at this point, the reader learns how deeply Lancelot's love for her runs. He is so tightly in Love's grip that he does not remember who he is, where he comes from or if he truly exists at all. All he has are the thoughts of his lovely Queen. The phrase "our knight" implies some feeling of ownership. This is due to the fact that it is at this point that the reader begins to fully empathize with Lancelot. From this point on, the narrator alternates using "our knight" and "knight of the cart." The names are not chosen randomly, though. For example, he is referred to as "our knight" when he thinks about Guinevere, when he rescues the girl from rape (lines 1101-1199), when he is honored, and when he grants the girl in the field's wish by beheading the...