According to the second version of the story, the ice cream sundae was invented in Ithaca, New York by a man named Chester Platt. Platt owned a drug store, which in those days often had a lunch counter and soda fountain. As the story goes, on a Sunday in 1893 he served a dish of vanilla ice cream with cherry syrup and a candied cherry to Reverend John Scott. In honour of the day, the Reverend named it a “Sunday”.

I learned about this fact from: http://inventors.about.com/od/foodrelatedinventions/a/Sundae.htm