Explanation of the expression 気が済まない


> A: 百均に入ると、何もいらなくても何か買わないと気が済まない人っているんだよね。
>
> B: いるいる。僕だよ。
>
> A: At the dollar store, there is always somebody who has to buy something
> even if they don't need it.
>
> B: Yes, yes! That's me.

I am told that 気が済まない means "won't be satisfied unless," or when one "must (do
something)."

If I translate the expression literally I get confused--

気 spirit/mood/feeling

が

済まない finish; come to an end; excusable; need not

Would anyone be kind enough to give me a clear and thorough explanation of
this expression? I think my main confusion is as to which verb 済まない comes
from.




sum-u has several meanings. The core meaning is for something to to come to an
end, conclude. From this, it also takes on the meaning for something to be
settled, at rest, or under control (as a result of something being concluded).
Putting this together, ki ga sum-u is "for ones feelings to be at rest / under
control", hence content. The negative form, ki ga sum-a-nai, is "for ones
feelings to not be at rest / under control", hence not-content.




sum-u has several meanings. The core meaning is for something to to come to an
end, conclude. From this, it also takes on the meaning for something to be
settled, at rest, or under control (as a result of something being concluded).
Putting this together, ki ga sum-u is "for ones feelings to be at rest / under
control", hence content. The negative form, ki ga sum-a-nai, is "for ones
feelings to not be at rest / under control", hence not-content.

