The title of this article is a conjectural. Though the topic is found within The Simpsons universe, a proper name is not available.
The Falling Couch couch gag is the first couch gag of Season 2.
The Simpsons sit on the couch. The couch then falls through the floor and Homer shouts "D'oh!", but only in 'Bart Gets an "F"". The repeats do not have Homer's D'oh.
This is the first couch gag that would later be used in another season (the next one is the first reused from another season).