Jehan is an old French from of Iohannes or John. Iohannes is Latin form of the Greek name Ioannes. Ioannese is derived from the Hebrew name Yochanan which means Yahweh is gracious.
John and the Jehan form are commons names but it seems that Jehan’s name is meant with irony. This is because he is a good-for-nothing mooch. However he does have Frollo’s favor at the beginning of the novel but he loses it when Frollo loses patience for his life style.
For the meaning of Frollo, please see my post on Claude Frollo’s name meaning
Considering the two Frollos are both killed by Quasimodo, does that make Quasimodo an allegorical King Arthur?
There another compontent of his name, Jehan Frollo du Moulin, which means “of the Windmill.” Jehan was raised at a windmillFollow thehunchblog