This became the norm for books and newspapers that had previously all been hand-written. Hand writing was not only time consuming, but did not leave much room for error. These printing presses now had the technology to record information and print it in mass quantities to share with the public by using these presses with letter plates.
Letter plates were small metal plates, each with its own letter, that were arranged on a larger plate to create full pages. In order to keep these letters organized, they came in a case referred to as a type case.
Type cases had small shallow compartments where the letter plates could be stored. Since most sentences have a significantly less amount of capital letters, these letters were stored in the upper part of the type case. The remainder of the letters were stored in the lower portion of the tray cases. That is the simple reason as to how upper case and lower case letters got their name.
