This is not a widespread term as far as I know but it is something that happens to me on almost any game that I have played in the past 20 years or so. I find a game, I love it, I play it for dozens of hours, I get to the late game content, it get's increasingly tedious and difficult, then I walk away from the game altogether and never end up completing it.
Time and time again this has happened to me and there are a few that really stick out in my mind.
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One game that really sticks out in my mind was a while ago and it was called Darksiders 2. The game was / is fantastic and has tight controls, a metroidvania appeal to it, and a kind of open world to explore. Just like you would expect from a game of this type is focuses very heavily on getting through various linear dungeons that feature a boss of some sort.
Late in the game you end up facing one of the truly difficult bosses and in this case he is nearly the 20th boss you have faced named Samael. The problem with facing this boss is that unless you knew the instance was coming up and saved outside of the room with multiple save-game files, the autosave is going to put you inside the instance with him and now you are trapped there with no way to go back.
I think I fought him 20 times or so, making a bit of progress here and there but ultimately giving up and saying that I would come back to him later. When I eventually did exactly that, several days later, I found that because at this point in the game you are using the entire controller during combat, the the encounter was even more difficult now that it is compounded with you forgetting what the buttons do. The action is fast at this point so there isn't much chance of you being able to relearn the controls without starting the game over. After getting your ass handed to you 5 times in a row, you turn the game off, leave it on your home screen for a few weeks, then eventually just delete the game altogether and never return to it.
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It's a real shame because at this point you have put many hours into the game and at least in Darksiders, the story tends to be quite good. I never did finish this game and it is so long that I think it is very unlikely that I ever will.
Other games have fallen into this late game loss of interest in my book and they even include some of my favorites like Metroid games, Witcher games, and even Zelda games. At this very moment I am nearly finished with Zelda: Skyward Sword and every time I sit down I have this moment of thinking whether or not I am really interested in playing something difficult, or if I want a more casual gaming experience.
I think a lot of it has to do with my age and the fact that I have other real-life obligations that I have to deal with such as feeding myself and that really annoying thing called "work" that I have to do in order to survive.
In the past 2 years there has only been a handful of games that I have actually played to completion and I think this is because of a combination of my age, the obligations I have in life, and the fact that I believe games are considerably more difficult now than they were when I was a kid. I could be imagining the last part though as games were pretty tough back in the NES days as well.
As far as Skyward Sword is concerned, I reckon that I probably need to sit down and play it today, else it will also just end up on the stack of games that I never finished and never will.