because the couch is usually set in front of the tv, it is the main place where people usually sit and watch it. lazy people would eventually seem to be stuck to it all the time. this person, a person who does not do a lot of physical activity, was called a "couch potato". this was also because potatoes do not move at all, and does not do anything but just sits there. this may also be considered as slang. couch came from the word "couche", which means, "a bed, lair," or from the word "coucher", which means "to lie down."