The Sunday that began this week is called Low Sunday. It is also called Quasi Modo Sunday, after the Latin words of the Introit, and yes, this is the same as the given name of the “Hunchback of Notre Dame,” who received it from the wicked priest who adopted him, having found the deformed Gypsy baby on that particular Sunday.
On account of the newly-Baptized neophytes taking off their white garments on this Sunday, it is anciently called Dominica in albis depositis. Lastly, and more recently, it is named Divine Mercy Sunday.
These various names can be related to each other. The words of the Introit come from I Peter 2:2: Quasi modo géniti infántes, allelúja: rationabiles, sine dolo lac concupíscite, allelúja, allelúja allelúja. (As newborn babes, alleluia, long for pure spiritual milk, alleluia, alleluia, alleluia.) They refer to the newly baptized, who are just taking off their baptismal garments (which, anciently, they had worn all week) on this day, and are encouraged to desire the rational milk of grace without guile. In addition to Baptism of the neophytes, the “second plank” of Penance traditionally has a place in the Sunday’s Gospel, and is directly relevant to the Divine Mercy revelations and the promise for Mercy Sunday.
Why the Sunday is called “Low” has been only surmised, but it is probably in relation to the comparatively “High” Sunday, the week before, of Easter.