Why are floors on a building called stories?

Why are floors on a building called stories?

ANS: Most buildings at that time had only one floor; churches being the highest buildings in a town. They had stained glass windows which had panes arranged in tiers that depicted biblical stories or events - thereby a storey being one of the levels of the stained glass windows. Later, as buildings came to have two or more floors, it was equated with the height of the stained glass windows in these huge medieval churches - i.e. 2nd storey being as high as the second tier of a stained glass window in the town church.