Cupcakes have been around since the late 18th century. The term 'cupcake' is mentioned in E. Leslie's Receipts of 1828. The name is said to come from the amount of ingredients used to make it - a cup full of flour, cup of butter, cup of sugar, and also because they were originally baked in tea cups or cup shaped moulds.
The shift from weighing to measuring was a big improvement when it came to saving time in the kitchen. And, its small size helped to insure even baking which was a difficult task back when baking was done on an open hearth oven.