Any fan of the Boston cream pie will tell you that it isn't a pie but actually a cake. The reason why this treat was misnamed is rooted in history when it was first created.
The dessert was created during colonial times when the words pie and cake were used interchangeably, as cakes were commonly baked in pie tins in the mid-19th century.
However, there seems to be some accuracy in the remaining part of the dessert's name. Not only was it first created in Boston in 1865, but it also uses pastry cream in its recipe.