According to the Grammar daily: 

Maudlin was first used in the early 1500s, and we get it from the biblical character Mary Magdalene. In medieval art, Magdalene was almost always shown weeping, either washing Jesus' feet with her tears or weeping outside his empty tomb. People of the time referred to anyone who has a similar weepy look or disposition as Magdalene. Over time, the pronunciation became slurred and the spelling changed to maudlin."