Largesse has a number of names associated with it, including charity, liberality, and generosity. It was considered a noble trait, and therefore knightly, to provide sustenance to the poor and distressed within one’s means, so long as it did not inconvenience the noble. This traced back to the Roman Empire, where wealthy members of the Patrician class would give small gifts of food or money to the people they patroned. This money would then help the plebeians they patronized buy food, access learning opportunities, and replace damaged togas. As members of the plebeian class, through industrious work or luck, rose to become nobilite (noble plebeians), they would often also patron those less fortunate or less successful than themselves.
Thus, it was considered important as a matter of the character of a noble, whether by birth or self-made, to voluntarily give a portion of your wealth back to the people, generally by patronizing those that had some connection to your family, or were working on a project you felt was worthy. Such patronage was the norm from the classical era though the middle ages, as barons and other members of the noble class selected freedmen to offer assistance to, or provide for artists, philosophers, or other early intellectuals whether or not they were directly associated with the church. In this context, while tithing was still the norm, the noble might also patron a specific monastery or convent that was dedicating its research and prayer to a particular subject.
There is more to Largesse than simple charity, however. Largesse was also a proscription against greed; while considered one of the deadly sins of the New Testament, that came later, as the groundwork for the Noble Habitus was laid long before the birth of Christ. Greed would tempt the knight into unworthy behaviour, causing him to conduct himself for the strict pursuance of wealth alone. While this was often forgiven of someone that was not of noble status, after all, most serfs and freedmen were lucky to have enough to eat most years, a knight would theoretically be in a position to have all of his needs pre-fulfilled. Therefore, while he may not have the wealth of the baron or duke, he was well taken care of and could pursue wealth through righteous conquest and sanctioned warfare, like any proper knight.
Of course, there was a practical side to this theory as well; a knight that was greedy could be bought off, and betray his baron or king, helping bring a rival noble or enemy nation into the lands of his Lord and assist in his overthrow. Such a knight, promised wealth or lands, which were the same thing in those times, would be considered beneath the contempt of his own serfs, and would likely be subject to invasion and rebuke from the allies of his former Lord. Unlike a normal turnover of land, the former knight, for no matter what title he carried he would have clearly forsaken his honor, would be targeted in ernest to be punished for his betrayal.
The purpose of Largesse was not to prevent a knight from accumulating too much wealth, but rather to remind him that he is responsible to the people he is Lord over and represents in Court. It also reminded him that when his people are healthy and happy, so are his lands, and his coffers.