How did the pillowcase come into being?

The answer is simple, in the late 1800's, early 1900's pillows were filled with feathers. They would stuff a sac with feathers and sough it together. Then they started making fluff pillows, which were a sac filled with fluff these pillows would get dirty so they added a case over it and instead of throwing it away when it got dirty they would put a case and simply wash it when it got dirty.