The use of “upper case” and “lower case” when describing capital letters or “small” letters comes from the early printing days. Each letter was made into a block. The block letters were placed by hand in a row to make words that would be inked and then paper would be placed on top of the ink to create the printed page.
The blocks were stored in boxes called “cases.” The printers separated the “capital” letters from the smaller letters to make it easier to find the correct size, so they decided to store the capital letters in a case above the one for the smaller letters. The result? “Upper” case letters are today’s capital letters. “Lower” case letters are our smaller letters.