Are you looking for this like this?
Reification/Reify
Value-judgement
Exaptation=take something initially formed in service of A, and apply it to B. Evolutionary science jargon that can be generalized.
Scarcity mindset
conscientiousness
Is it the words or the concepts that you're interested in here?
There's obviously a lot of value in having e.g. the concept of "confounder" available to you, and if you knew of it but were in danger of forgetting it then it would make sense to try to get it better fixed in your head. But if you have the concept of confounders, but were in danger of forgetting the word, it seems to me like that matters much less. Your thinking won't be too badly impaired by having to replace "confounder" with "wossname", or with "something irrelevant that produces similar effects to the thing I'm interested in", or whatever.
So are you looking for particularly valuable concepts that have single-non-jargon-word names, or are you looking for cases where the words themselves are valuable (e.g., because it's extra-useful to be able to use them in discussion with other people)?
What do you mean by "plain language"? I think all of "corollary", "stochastic", and "confounder" are jargon. They might be handy to use in a non-technical context too (although I question the use of "stochastic" over "random"), but only if the reader is also familiar with the jargon.
I also wasn't familiar with "mu" at all, and Wikipedia suggests that "n/a" provides a similar meaning while being more widely known.
I don't know what I mean by 'plain language'. It may be a misnomer. Here's my first guess:
If it wasn't invented on LessWrong or the ratsphere generally, requires no fluency with mathematical notation beyond arithmetic to get familiarized with, can be explained in less than 400 characters using only words that a median WEIRD 15-year-old has a 1/3 or greater chance of being familiar with, and it seems great to remember, then I will include it on this list.
I once spent a lot of time trying and failing to remember the word 'corollary', and once I heard it again I was like "ah, finally, there's that word; now I won't forget."
What are some other words like this? I'll keep an updating list in this post as I find and think of more of them.
Suggestions from me:
Suggested by others, approved by me: