A lovely Jewish woman was to be wed to a handsome Catholic man. Traditions were equally important to both families and this made choosing a theme song for their wedding a major challenge. The groom's brother had a rich operatic voice and was especially noted for singing Ave Maria. The bride's Mama, realizing the dilemma sighed and said "Oy vey!" "That's it!" replied the groom. Oy Vey Maria was jubilantly sung.
Source: Someone told me a simpler version of this when I was a child. They had simply asked "What song is sung at a Jewish/Catholic wedding?" The answer, of course was, "Oy Vey Maria." The embellishments are my own.