Think of interest as a thread running from you to a thing. Dis- cuts the thread. But English interest is really two threads wearing one name: one is curiosity, the pull that makes you lean in; the other is a stake, the share that means you gain or lose by what happens. Cut the first and you get someone who is not drawn in at all. Cut the second and you get someone who has nothing to win — which is exactly the person you want counting the votes.
From the word’s history
The word is simply dis- plus interest. Because interest already carried both the curiosity and the stake, the prefix produced two meanings at once, and English has kept both.
這個字就是 dis- 加上 interest。因為 interest 本來就同時裝著「好奇心」和「利害關係」，這個字首一加上去，就一次生出兩個意思，而英文把兩個都留了下來。
Wiktionary entry for disinterest (packet source_ref kaikki:3f6f69a190036ae4:1184240695:17653): “From dis- + interest.”
登入就可以看每一支怎麼連回核心畫面。