Why is Sundae called a 'Sundae' ?

What is it?
The sundae is an ice cream dessert. It typically consists of a scoop of ice cream topped with sauce or syrup, and in some cases other toppings including chopped nuts, sprinkles, whipped cream, or maraschino cherries.

Trivia
It was once unlawful to sell fizzy drinks on Sundays. So soda shoppes served, ice cream treats instead, "Sundaes".

Origin
Origin of the term sundae is obscure, however, it is generally accepted that the spelling "sundae" derives from the word Sunday. the dish arose in contravention to so-called blue laws against Sunday consumption of either ice cream or ice cream soda (the latter invented by Robert M. Green in Philadelphia, Pennsylvania)in 1874. The religious laws are said to have led druggists to produce a substitute for these popular treats for consumption on Sunday. According to this theory of the name's origin, the spelling was changed to sundae to avoid offending religious conventions.