Well, they were originally called Motivational Posters and were manufactured by some company. But that was during the time when they were serious and unfunny. Eventually the internet started making parodies of them and so the
Demotivational Posters were born, but then some capitalist prick smelled a chance to make money by using the creations of others and started selling
Demotivatiors. A lot of people still call them by their original name, though.
