All The Tropes:Trope Decay
Sometimes, the idea of what a Trope is actually about gets lost somewhere along the way. Either new entries miss the point somehow, or the author just read the trope title and thought they got the gist of it. This includes things like describing just anything remotely scary as Nightmare Fuel, when Nightmare Fuel was originally intended to be things you found unintentionally scary as a kid. (Hence why Accidental Nightmare Fuel was created and Nightmare Fuel repurposed) Remember though, that Tropes Are Flexible—what you think is decay may just be unusual usage on second glance.
A good example of Trope Decay in action at one time could be seen with Not Allowed to Grow Up. This trope was originally about early live action Sit Coms where the situation was so strictly defined that the real children in them could not be allowed to grow up lest they destroy the show's dynamic, a practice that culminated with the sad case of Anissa Jones from Family Affair. However, it was quickly taken over by hundreds of breathless revelations that cartoon characters don't age, and the Family Affair material was exiled to an analysis page in August 2011. (However, in 2017, the trope was rewritten and rescued from decay. Check its history if you're morbidly curious as to where it had gotten to, though.)