I found [1], created all the way back in 2021, which seems to first introduce this "kidney disappointment" term, and I would have to assume that perhaps the authors preferred to translate it from their native language.
LLMs did not exist in their current form in 2021, so couldn't have used it to write down a coherent thought, let alone a paper, at the time.
At the same time, I do live in the same country as the authors, and while we don't speak the best English, being a student at a college without some familiarity of the English language to come up with the term "kidney disappointment" is, let's just say, hard to believe for me.
Edit: This other comment[2] made me realize what it might have been: plagiarism avoidance.
Unfortunately, many colleges here do not have the best reputation and often run like degree mills, and the aforementioned comment made me remember a conversation with a friend, who mentioned writing a review paper.
Again, LLMs were not really a thing at the time, so they mentioned how they had to run their paper through a plagiarism detection tool, and then they substituted words with their synonyms. I guess someone really did search for the word "failure" and found "disappointment" as an alternative.
[1] https://www.researchgate.net/profile/Suprodip-Mandal/publica...